Why are guys who have multiple partners and one nighters really y?

Its like wow- u put ure thing in a girls u know- who cares. It like they think they've found a cure for cancer! I've seen this in a lot of guys. They've believe themselves to be living life to the full when really there just shagging people who they don't give a **** about- the idea just repulses me. Also they are less attractive to a girl if she knows they have done this and usually u can tell by the smug look on the jerks face! Slimey, inconsiderate w**kers! this is my opinion.