Part of it is because he's never really been a knock down perimeter shooter. He obviously took, and made a decent amount in high school, but he was a much more all around player, than a shooter. He's never been a guy that shoots a lot of perimeter shots off the dribble either. And in Woodson's system, if you're not confident taking shots off ball screen actions, it limits your looks dramatically.
I think if he were playing in a system that produced more kick out catch and shoot shots, he'd take more of them.
I also do think he's smart enough to know he's not a knock down shooter, so keeping the ball moving, and finding his shots in other ways is what's best for him, and for the team.