The "normal physics" of pressurization and our understanding of atmospheric containment don't apply in a galaxy far, far away... (IMHO)
Because TIEs make noise in space. ;-) And have to bank and turn like an atmospheric craft...
Why? Because... STAR WARS...
...baby.
So at some point, someone in some TV show will fly a TIE into open space without a helmet on, and there will be much ado about having to "retcon" things and people wondering what it could possibly mean...
...while the author just wanted to have a cool story about a dude stealing a TIE fighter.
