I think details such as the TIE pilots having spacesuits on comes down to two things;
- Suspension of disbelief. Even in something has scientifically illogical as SW there’s a requirement for certain familiar imagery since the setting is already recognizable as sci-fi. However since it’s not really important, they manage to stretch that logic in the scenes where it’s more obviously fantasy/myth inspired, e.g. the space-slug, anything Force related, etc.
- Aesthetics. Like I’ve said before SW seems to often just goes for what looks cool and interesting. Also it’s important, especially for the kids, that the stormtroopers remain faceless, both to make their deaths seem less violent and for its symbolic value. And since there’s not much reason for someone to wear their armour inside a fighter, the Rebels simply wear helmets after all (even though a space suits would make more scientific sense, but they’re mirroring WWII fighter planes not real space travel), they simply added a space-suit-armour allowing them to make even the TIE pilots as faceless as all the other Imperial grunts.
I do see your point there. It’s well thought out. I especially agree with you on the notion of making the bad guys being faceless – it makes it easier for the audience when they are killed and it makes them look more menacing.
Still, however, I think space fantasy has its limits. Humans floating about the vacuum of space goes over the line, in my mind.