They play soccer and lacrosse because they are not athletic enough to for football or baseball. They have almost no muscle mass, most can barely bench 135. The So Cal Bro's arch nemesis is the jock.
While taking a backseat to the jocks in terms of high school popularity, most So Cal Bros join fraternities in college in an attempt to boost their social standing. They have success in frats due to the fact they will do almost anything to get some pussy.
When it comes to girls, a So Cal Bro will typically play the "best friend" role. He may put up with a girl's shit for years and not get any pussy, only to wait until she is at rock bottom to make his move. After a girl has been played one too many times by "douche bag" guys, she will inevitably give the So Cal Bro, her "best friend", a chance.