Much simpler explanation than that. 1) It is much easier to make your shot around the basket because, duh, you're closer to the rim. 2) You get 150% as many points for a three point jump shot as a two point jump shot, but it's not 150% as difficult to make that three pointer.
That shot chart reminds me of every rec league I have played in. Either you shoot you a three or get to the hole.
