I feel ya Raype, but they took a design choice and it kind of payed off. I mean who now (If you've never played RE1 or it's remake) even remembers Jill ever wearing any official S.T.A.R.S gear? I bet you very little would even go back to even see that either. So Miniskirt Jill it is.
I also get you on the wear sensible clothing woman, you're in an ZOMBIE OUTBREAK!
But with the ways the RE movies portrayed her, it's like continuity and coolness, what's that?
(Plus Ashley and Aya suffered from the same stupid flaw of no pants, at least in the normal play-through in RE4)