Good for the Celtics. Doesn't make any sense for Jackson. Good for MSU.
He has been a consistent riser all winter, why would he want to try it over under more scrutiny? Either he is hearing that he isn't as touted as the media said, or he's not ready to give up on the school life.
He definitely will benefit from another season at MSU. He would have a chance to lead, improve his defensive positioning to avoid excess fouls, and take a bigger offensive role. Those are all things he wouldn't get going to the league.