because he's trying to make a 'race messiah' of himself. Seems entirely fathomable that he believes he's worth more than league minimum, and that's why he didn't accept.
And he's probably smart not to. At some point this year, due to injuries or some other weird circumstance, a team will be desperate for a QB--and he'll be the obvious choice for that team. And when that happens, he'll get more than league minimum.