Some men are because us girls are just sooooo dam good looking that they want us to see there muscles.
Yep. It's called peacocking. It generally why the male of a species is more colorful and beautiful than the female.
Attracting a mate. So yes to answer your question. Males are hard wired to flaunt in front of a female.
of course they are. and society provides tech support.
Some are. They tend to either be insecure or remorseless douchebags.