Because America is the Land of Opportunity, and we theoretically don't believe in this class-based removal of opportunity.
If the big schools want to keep their spot/prestige, let them continually earn it the same way as everybody else, and level out that playing field.
We all play under the same rules (for now). That doesn't mean we shouldn't have the ability to look out for our own self interest. There is nothing unamerican about that.