I don't know how many people are going to read this, but I thought there should be some sort of theory going on to try to get the board some more posters until Jim gets caught giving total control of 8kun to reddit mods or dancing to Ariana Grande in a tutu or something else that would prompt an exodus here. Also I'm locked in because of Corona-chan's rampage and have nothing better to do.
For as much as we need to have a new space thread and other threads, nobody ever had this on the old board, so we should use this thread as a general clearinghouse for everything involving land battles. We had a brief detour in the ship thread on the old board about land vehicles. It was mostly about why the Rebels use tanks and the Empire mostly uses walkers. I came to the conclusion that it was partly because Imperial arms companies wanted to milk the Empire for as much money as possible because walkers are high-maintenance, and the Empire wanted to send a message to the Rebels that they can afford to splurge on walkers and still have much larger armies. But there may be other reasons. Tanks will generally fail in cities, forests, mountains or anywhere else that isn't open and largely flat, while walkers do better in places with terrain that tanks find difficult to negotiate. The Empire is situated in the heavily urbanized Core Worlds, while the Rebels are stuck on the outskirts of civilization making limited forays into Imperial territory. That means walkers are better for the kind of terrain Imperial armies occupy and vice versa.
But there's the strategic aspect of it as well, and I don't know if that belongs in here. It involves when and how land battles would even take place to begin with. Whoever has control of the local space will usually either bomb the planet into submission or they'll be up against planetary shields and batteries that they can't get through. The only exception to this is when only some of the planet is covered by shields or planetary batteries, which is rarely the case on major worlds, when the planet has little to no civilization to speak of and troops can be landed with no hassle, or when only a certain part of a neutral planet has anything worth having, which is also quite rare. So the only way most planets would ever see troops landed would be in cases like a fugitive Jedi hiding out there rather than legions of tanks and walkers slugging it out. Planetary assaults are commonly depicted as short-term affairs, but historical sieges lasted for years or even decades, and sieges are the best analogy for attacking a shielded planet. It takes enormous resources to take and hold a planet.
There's also the problem of how standing armies got started to begin with. We know that there was no standing army in the Republic prior to the Clone Army, but the KotOR era depicts the Republic as having a standing army. It may be that the Mandalorian threat of that era prompted the swift raising of an inevitably inexperienced army, which would explain why they were sitting gizka in the face of the Mandalorian assault and had to have Revan rescue them. If this was the case, the Ruusan Reformation would have reset the Republic to having no standing army. Of course, the Republic relied on the Jedi for protection, but as Mace Windu pointed out, they're peacekeepers and not soldiers. The Jedi's combination of their powers and superior diplomatic skills can suppress minor threats with ease, and the overall strategic situation is more favorable to limited land battles anyway, and the smaller the battle, the more each individual's performance matters. This explains why the Jedi were so dominant for so long, and therefore why it's so uncommon to find people using slugthrowers or anything else that's good against Jedi when by all rights everybody should be using them or at least have a special cache of /k/'s favorites handy - the Jedi benefit on both the tactical and strategic level. But they become less useful if a major war has already broken out simply because there aren't enough of them. The most powerful Jedi can easily decimate even the best mundane soldier unless they're up against an overwhelmingly large army without support. But the Jedi can grow complacent and lose power, and according to my reckoning, the best way to verify that this has happened is the mere existence of an army.