Actually guys that are like that were made that way by women who were *****es to them.
Sex isn't even that good for guys it's sort of disappointing in the end but during it you feel good as in it makes you forget whatever crappy thing some girl that broke your heart done, that's why a lot of guys become manwhores, to take their mind off being hurt.
So they become all about sex and not about feelings.
Men may be worse for that but women are way worse for lying in a relationship.
I find it annoying when girls moan about guys being dicks when they go out with "badboys" etc who are clearly not nice all the time.
If you want a nice guy DON'T GO OUT WITH A GUY THAT ISN'T it's quite simple.
Also most girls tend to friendzone nice guys then moan when all they have left is dicks, who's fault is that?
Friendzoned people may be weird, but at least they would be devoted to you.