agree with wdleehi; he's got lots of great tools already, why not add another?
I also think there is an element of 'stashing' going on as well. Potential trade partners are actively scouring the league, and the less time floor time Smart see's between now and Feb, the better it is for Ainge if he ultimately wants to keep him out of deals.
Meanwhile; guys like Sully, Bass, Rondo, Green, Thornton, and AB appear to be on showcase...
My opinion is, based on what I've seen thus far, Ainge's next-gen celts team will feature Smart as pg and captain.