Because Stormtroopers are functionally heavily militarized colonial police more focused on enforcing a terror regime than fighting against peer militaries, and the Rebels are more or less the singular exception. Same reason that wearing typical riot body armor IRL is unlikely to keep you from getting fucked up if someone’s shooting .308 at you.
While I wouldn’t put it past Google/YouTube to do something as shitty as this, I think people are far too quick to assume foul play over the much more likely possibility that the world’s largest video platform occasionally shits itself.