Why Walkers Exist in Star Wars

The true answer: if Lucas thought it looked cool, it went in the films.

Building off the discussion of the space battle of Naboo, the fact that the Droid Control ship HAD those massive open hanger bays that Anakin could fly into makes perfect sense if we consider that the TF ships are clearly NOT purpose-built warships, but rather converted cargo-haulers that have simply had military-grade shields and weapons bolted onto them. Why wouldn't you want big, open, easy to access hanger bays on a ship meant for maximize cargo-loading efficiency?

The episode 2 incredible cross-sections (canon or not) explicitly states: "AT-TES are effective at penetrating powerful energy shields. Walker movement uses simple surface traction, whereas the high-velocity exhausts that drive a speeder or starship are stifled by particle shields. Furthermore, flying craft can be damaged by energy discharges leaping from the ground at shield interfaces, but a walker's natural grounding provides invulnerability against this effect. AT-TEs are also well shielded against electromagnetic pulse weapons and ion cannon fire."

From the Star Wars Essential Guide to Vehicles and Vessels (literally on the first entry, which is for the AT-AT Walker): "while the empire had countless repulsor lift vehicles, drive systems could be foiled by gravity fluctuations, unusual planetary magnetic fields, and other special conditions; the empire needed a vehicle which could be used on any terrain on millions of different worlds."

hangardoor shields are clearly set to smths like "let everything through except atmosphere"

What I've always assumed is that energy shields interfere with antigravity technology, and if something were to attempt to hover through a shield, the repulsorlift would short out and the vehicle would drop like a brick - basically, what happened in that one mission in Halo: Reach when the helicopter tries to fly through that shield to get to the Covenant tower. I'm not so sure the Trade Federation ship failing to seal off the hangar bay was an accident - they probably kept the door open so they could launch additional droid fighters as needed, while assuming that no human pilot would be insane enough to try and fly INTO the hangar. Doing that at high speed without being able to see what's in there until you're already inside is a very good way to crash, and the last thing a pilot wants to do is sacrifice his maneuverability like that. Anakin only got in there by accident, and managed not to crash because at that point, he was just redoing the podrace.

The slow blade penatrates the shield.

The Droid vs Gungan battle always makes me think of them battling on the Windows XP wallpaper

That thumbnail made me realize that while we have seen an AT-TE go up against an AT-AT, we haven't seen an AAT vs. AT-AT. The AAT probably wouldn't fair well, it would be an interesting exchange.

This reminds me of the lore for KOTOR how personal energy shields were so widely used for blaster protection that vibroblades and other melee weapons were standard issue simply because one shielded opponent could charge another and use their melee weapon to physically pass through the shields

There’s also a couple more factors, repulsorlifts can be jammed. Repulsorlift countermeasures have existed for a while in the EU but they were directly mentioned in Rise of Skywalker. Additionally, weather seems to be a large factor as in the older Republic comics the Republic Army had to ditch their repulsor tanks on Jabiim due to the weather and had to switch to walkers, including prototype AT-ATs

I always like seeing technological and tactical evolution in settings, and the idea that the Naboo invasion revealed several weaknesses in a largely repulsor vehicle-based doctrine that lead to several changes in how repulsor and walker vehicles were used, tactical innovations that came with trying to defend against both, and the calculated risks in favoring one over the other makes for a very realistic, interesting, and living setting. We see this constantly in real-world history, and putting it in fictional ones makes them all the richer. Plus, it's a good excuse to keep rolling out new vehicle and weapon designs and battle set-pieces as the story develops over the course of several in-universe years to keep things fresh and interesting.

The repulsor lift and show don't tell point reminds me of another thing in Star Wars, people go "Well gravity doesn't exist up there in space.", which presumes all ships are in orbit, and is an assumption that would fundamentally change how Star Wars battles work. Yet we clearly know that even larger ships like Venators, corvettes, and now ISDs all use some sort of tech to fly relatively close to a planet, which is probably replusor tech. This is demonstrated not only in how combat is depicted more naval-like than something more Expanse-like, but in how crippled ISDs fall back to the planet or other gravity source.

2:26 "Good thing you remembered the shield's deflection capability's directly proportional to the amount of kinetic energy directed at it." Samantha Carter, Stargate SG-1 😂

I think it’s fair to say it’s because walkers are cool

I think the key is that the “slow moving object” is also in constant contact with the ground. As the shield begins at its highest point and then forms a dome over the generator, an object “passing through” while in contact with the ground isn’t so much penetrating it as it is interrupting it from reaching the ground and effectively making a temporary breach. You can even see that the battle droids only experience significant resistance until their legs are through.

6:34 THat's not entirely true, all ships have a particle shield close to the surface across most of the vehicle. We see the Trade Fed control ship antenna surviving multiple proton torpedo hits because of this. They're called Shift-shields in the ANH novel or older script, the Tantive IV's are disabled before an asteroid collision is faked to throw the Senate off the trail for a little longer (Which means the shields prevent collisions). Even in the film sort of implied by the Death Star briefing saying the thermal exhaust port is ONLY protected by a Ray Shield, implying the existence of a shield that stops solid objects, but was left off the thermal port either due to an oversight, or because the other type of shield would trap in the hot exhaust that it was meant to vent. the DS2's shield would have crushed the entire fighter force had Lando not realized they needed to pull up. Anakin went through the open hangar bay particle shield likely because it didn't come back up fast enough when another fighter wing left the hangar

I think the X-Wing novels also covered the esoteric nature of shielding.

i always just thought it was a electrical grounding effect. like if you are in contact with the ground you can push through the surface tension. also id like to point out the droidica couldn't use shields while rolling at speed and generators on Naboo had to be kept steady or they would . honestly its a good way to keep ground forces from being obsolete in a space age.

I always assume the Ray+particle shield combo works somewhat similar to how they are depicted in dune. The shield component that stops energy is actually "skin tight" to the ships hull, as it presents the smallest target profile possible in an engagement. However, the component that stops actual projects works by reacting to kinetic strikes, so they are only react when something strikes with sufficient force. The reason for this might have to do with exhaust leaving the ship, air and light exiting and entering the bubble for flight and navigation respectively, or whatever other purpose. It also explains more or less how proton torpedoes work, in lore they are noted as being slow enough to be shot down, hence why they are fired near point blank, but they also have the characteristic red glow, which some sources paint as an energy field. So the way a proton torpedo works is it goes slow enough to the target that it's energy field allows it to bypass the shield. If they went faster, or didn't have that field on they'd just slam into the particle bubble. This brings me to my final point, the projector also seems to have an influence. We've seen shield type technology be used for jail cells or bridges. It would seem that when the projector is outside of the object or has an connection point opposite to it it's possible to make a thicker barrier that impedes physical objects to pass through. This would also mean that depictions of shields like in Squadrons or the Rebel fleet in TLJ aren't entirely accurate to how the average shield operates.