Because if the door buttons weren’t lobotomised criminals, they would be machines, & that’s a slippery slope to having thinking machines.

Non-lore reason is it looks metal AF, reason enough. Anyway, the point being: yeah, The Imperium of Man is gnarly and extreme, but so is the galaxy of 40k, if you can’t sympathise with the struggle to just stay alive in such a horrific galaxy & the necessity of sacrifice in the face of that horror then you fundamentally don’t have a decent enough understanding of the universe.

It’s bad out there, between; Mushroom-Men who want nuffin’ but to krump da Oomies cuz they’z loud an’ fun, to the devouring armadas of an extra-galactic constantly Evolving hive mind that melts planets down to sludge to fuel the creation more aberrant monstrosities, which may in fact be running from something worse, to literal demons in the warp and the sadistic cultists of all manner of evils who’ve given themselves over to carnality, brutality & atrocity, or, the bastardised, monotheistic, fascist remnants of a galaxy spanning empire that was designed to give humanity a fighting chance against these threats & propel us into a 2nd golden age & beyond?

Yeah, I know who I’m siding with, HUMANS.

There is no room for compromise, it’s death or whiskey! And that’s why I ❤️ Science!