How come sports only pay attention to div 1 athletes?

I mean I think the NBA draft Is not fair question how can u enter the draft if your a div 2 or 3 players back to the NBA they only pay attention to div players it's stupid just because they didn't go to the Kentuckys and dukes doesn't mean u can just ignore them also do the undrafted players become free agents or do international scouts offer them to play international