Why? He played well enough in college for an NBA to pay him 4 million guaranteed in the hope he develops a more all around game. I do not believe colleges develop NBA players better than the NBA would.
I'm not very surprised that he sucks. He shows plenty of that last season. It's just that the Pelicans exercising his contract's option, and his decent showing in the preseason (at least in the 2 games I've watched) seem to point to a positive direction for his play.
He just got extremely overrated because everyone thought he did the one thing everyone in the NBA wants and looks for, creating shots. I know I wanted the Rockets to draft him because of that reason. But it turns out that he is only a pretty good shot creator but a poor shooter and finisher. And if your only positive is shot creating but you can't finish the shot in the NBA, you aren't going to get time. He is still a young player though, so he will get his chances somewhere.