I'm pretty sure its just part of his image
Maybe because he's been through a lot.
Because he eat to many sour skittles and he become sour.
He's been through a lot in his past. He just doesnt want to smile for personal reasons.
He's trying to project an image of a tough streetwise urban rapper and I reckon that smiling makes that image less intense or strong.
Well because ov the tough times hes been throu .. But stil he smiless n it makes me fall in love wiv him sooo much
Ive always wondered tht too...apparently sum of his fans say he does....his older songs he seems mre jolly 8)
Causse when he is rappen theres no smiles he is being real and bustin out the reality of the world