It's cos guys are all about being macho and having a finger in their ass would probs make them look gay, and for some reason they are scared of liking it and becomming gay and it goes on and on...

Its mainly because blokes thinks its a bit wierd, its just not something i'd enjoy personally, and i dont know any girl who'd wanna finger a bloke... I mean... do the girls wear gloves or what lol?