> But why? why can't it be an option?

Because universities have decided (rightly, IMO) that just taking the applicants with the top GPA and SAT scores and no other criteria doesn't give a very vibrant student body.

Chances are a school like Harvard already has more "top student" scorers in this fashion than they can accept.

> How do you work on something that you have no control over?

"God, grant me the serenity to accept the things I cannot change, Courage to change the things I can, And wisdom to know the difference."

There are plenty of things you can work on that colleges love to see. Volunteering, neat science projects, interesting life experiences, sports and performing arts, etc.