Always and Never seldom apply to anything! A boy might ask him self, "Why do I always choose girls that cheat on boys?"
However I think it's important to note most boys and girls are (pretending) to be adults when it comes to relationships, love, and sex. The vast majority of them lack the maturity to commit to a monogamus relationship. In fact most parents do not want their teens spending (too much time) with any one boy or girl because it often leads to sex. In essence parents would rather their child date multiple people and do "group dating". When you get older you'll look back and see how unrealistic it is to expect a 13, 14, or 16 year old to "foresake all others". At that age no one has figured out who they are or what they want and need in a mate!
One additonal sad note is too often kids become too "emotionally invested" in these relationships. When I was in Jr. high a 13 year old girl attempted suicide because her 14 year old boyfriend dumped her. A 30 year old woman I know recently told me she finally got (closure) from a man who broke her heart when they were (15 year old) kids!
No one that young should believe their world revolves around a relationship and no one that young should be held responsible for another person's well being! Truth be told the vast majority of us do NOT end up marrying our Jr. high or high school sweethearts. Dating at those ages should simply be about having (fun) and not trying to find a spouse! One man's opinion! :-)