Why are girls so shallow ;/?

It has nothing to do with you, so your self esteem should not get hurt. Girls are just stupid, plain and simple. They go for the bad boy, the one one who will cause drama in their lives. No clue why, but girls like a certain level of complicity in their lives. Once they hit a certain age, they begin to see that a nice guy like you has slipped away and is with someone who appreciated him from the start. Hang in there. You seem like a sweet guy and you will find someone who appreciates you and loves you. Til then, enjoy your life.