Do you think she wears that while she's piloting an F-18? Or parachutes wearing that?
Unless they don't have time, they are permitted to get changed. Uhura put on Starfleet coveralls
to get underneath her communications station in TOS. The only time I can recall a woman in ST wearing her highly impractical skirt uniform for very dirty duty was Marianna Hill, as Dr Helen Noel, crawling through a shaft in TOS.