I'll tell you why guys suck.
When they're into a girl, they try their best to "get her". The cooler the girls act, the more enthusiastic guys become.
And when the girls become their girlfriends, suddenly all things change. They become "less precious", "less valuable", just because they're already "taken". The guys suddenly start to flirt with other girls and ignore their girlfriends whom they were so much in love with before.
Don't believe me? Try to observe.
s17