I think part of it is that he doesn't like to be perceived as just a shooter and sees himself as a "fully fledged" basketball player, who can do more. He's just trying to make the right play every time and seems to diminish the value of his own 3-pointers in his mind. He does make many good plays outside of the sniping BTW, He seems to have a pretty high BBIQ. This isn't to say I wouldn't like him to shoot more, but I think I kind of understand him and it's not as bad as it is psrceivrd to be, because ge usually makes a good play (even if not the perfect one).
