Why do men not wear lipstick?

Because they're afraid to. They think people will assume they're gay if they wear any visible makeup at all...and guys don't want people to think they're gay. (Note I said "visible" makeup...a LOT of men have discovered the benefits of covering up dark circles under the eyes and age spots, but that's about as far as most guys will go.)

The strange thing about this "men who wear makeup are gay" theory is, some of the male celebrities who draw women to them like magnets, like Prince and Elvis, wore a lot of makeup. Elvis liked blue eyeshadow, James Dean wore mascara, Prince wears a ton of product...