Men can seperate sex from emotion. Sex for a man can be a physical act without any sort of emotional connection. I'm sure there are women out there like that too but a large percentage of guys are like that.
The men that do it are just not commited to one person, they don't have the strength to say I am with one person and one person only... <br />
However women are just as bad, and I agree with ianlarc, not juts because us men stick together either. You yourself may not cheat on the guy you are with, but there are so many women out there that do the same thing if not worse. Where I am from the women are worse then the men, and believe me thats the truth; Do you want to know the reason why women haven't got such a bad name for themselves? because unlike the women, men do not go and tell all of our friends and post it all over our social network statuses. We just get on with it, start again and find someone else.
I used to be able to do that. Then at some point I grew a conscience. Sucks.
They just do.<br />
First you would have to confirm that your relationship is an exclusive. If they tell you up front that this is NOT what they are looking for then let him go. <br />
Females I feel want permanence. It's unusual for a female to back away. Even when their is abuse involved. <br />
Women need to know the signs and get out before it will hurt us more. Ask another question of the Males. What are the signs when you want to end a relationship.
The answer is dnt get to damm attach to the guy until he shows you he cares.!
They just don't see it as a big deal. They figure that they'll get what they want and that the girl will get over it soon enough. I guess they're not good at committing themselves to one person at a time, maybe don't see a reason for it. They might see their other guy friends doing it and think it's alright for them to do it as well...And it's more fun for them I guess, probably gets boring being just with one girl.