Interestingly, and this was on Singapore Air and/or Qatar Air, can’t remember which, they greet you with the mini-skirt, then before serving change into a different uniform with slacks.
Those ladies would look lovely in anything. Why not leave them in something comfortable all the time? Not to mention the time it takes to do a quick change. Even if it’s just sliding off the skirt and pulling on a pair of trou, that’s time away from the rest if your dutues. What a PITA.