For the same reason people generally wear business attire when they are at work. It projects an image and that image in an aircraft is one of professionalism and authority. For all those who travel as SLF the survival stats favour those who have paid attention during the brief and have some idea of what to do if the worst happens.
Sorry, but the airlines have constantly used "sex" to promote their services.
The poster made a comment that inferred s/he liked looking at the attractive crew members.
If survival safety was the ONLY consideration, the crew would be wearing nomex clothing oriented to that consideration.
e.g. grobags, not skirts.................
My point is that people on this board make naively realistic and absolute utterances which are complete b@llocks.
Of course the cabin crew are trained in safety and BA038 is an example of great work when confronted by an unbriefed and unexpected situation - my hat is off the that cabin crew
But to make absolute statements that the crew is there for safety only and not for the passengers comfort or indeed to be easy on the eye is patently the opinion of someone incapable of grown up thinking.
PS: for the avoidance of doubt, please give a clear and unambiguous definition of "business attire"