The modern trend in adult films - especially American - is for men to be pretty much hairless all over, and pretty ripped as well - people like Ron Jeremy excepted of course.
It's the same principle as a man shaving off his moustache, and finding his nose looks bigger - if you catch my drift!
If it's your job - fine, but I think that for individual men, it's a personal choice, and personally, I have no particular desire to look like the last turkey in Tesco, so I'll stay as I am.