Why do guys stare during sex?

I know this may sound stupid but it's really something I was wondering about. I was having sex with a guy yesterday and he was staring at me while he was on top. This didn't really happen when I was with these 2 other guys they did look but not for as long. Anyways I'm not dating the guy though and this was our first time having sex together.
Why do guys stare during sex?
Post Opinion