There’s a little detail in Tie Fighter media that I like, where the Tie Fighter pilots love the fact that they don’t have shields or any fancy fly-by-wire stuff in their fighters because it makes them “real pilots”, compared to rebel pilots who have astromechs, shields, and hyperdrives. Extrapolated out a bit, and you could interpret the Empire as constantly sabotaging its own military effectiveness because of a toxic bravado that has been allowed to infect its military at all levels, which is pretty compatible with the Empire’s implied fascist ideology (that the movies don’t go too much into detail about).

So storm troopers could have Heinlein-esque power suits, but they all think that having something like that is for wimps, all the way up to the top of the chain of command.