I don't think all guys are the same... but most of the time its because they haven't found or taken the time to get to know one of the guys that is different. Sometimes it's easy for girls to overlook the good guys.. which is unfortunate. For some reason especially when we are young its the bad ones that we are attracted to.
It's not all girls. Also because most men and boys these days don't really understand or know how to treat a girl or women right these days. It's just that with every girl's experience added together would probably be about the same experience
Well they often copy their friends when they are around girls, because they want to make sure that they are doing the "right" thing. But guys arent all the same! There are jocks, nerds, greasers, preps, etc.!