they can, (go on, go try...) It [tends to be] not socially acceptable.
Because men don't have mammary glands like women do and in some societies (including the U.S.) a woman is not aloud to show her...
Depends what type of body you have! If you want to look good, then you want the smallest bikini you can manage, especially if you are a little extra curvy. More fabric just makes you look bigger...