I suppose it’s a stylistic choice, it would be awkward if they had episodes of Deep Space Nine or BSG where the main characters stopped what they were doing to try and squeeze into a space suit. The helmets themselves would also hide the actors faces, which would make it impossible for them to convey emotion. On the other hand, mil scifi novels wouldn’t have either problem, since it’s nothing to just drop a mention the former and the latter is a non-issue.
Of course, it would probably be uncomfortable to wear a helmet nearly all the time, but there’s an easy fix: awesome tech! Okay, maybe not call it that. In the big screen adaptation of Lost in Space from the 90s, Matt LeBlanc’s character had an awesome helmet that would wrap around his head on command. A sufficiently advanced tech level could have the same type of helmet, store in the suit itself and keyed to deploy as soon as one of the aforementioned situations arises.
A neat idea would be to give the helmet some enhanced functionality when worn. A HUD could be displayed on the faceplate.
Hmm, I’m definitely going to have to file this away for future worldbuilding use.