Why do men like sexy lingerie on women, but it is rather unusual for men to wear sexy lingerie themselves? What is the background to this, and how will it develop?
It's not just about liking sexy underwear - although that definitely plays a part. It also comes down to societal expectations around what makes someone "sexy". For example:
- Men are taught from an early age that they need to be physically strong in order to protect their woman and family (i.e., manly)
- Women are taught that being sexually attractive = having curves, breasts etc...(i.e., objectifying women). 
When both genders follow these stereotypes there can often be friction between the sexes as one gender tries to live up to society's expectation while the other doesn't.