He wants the best contract to be a starter for a winning team. If that were possible here, he'd stay, but the Celtics roster and the salary structure of the NBA is going to make it impossible.
Terry would accept 2 out of 3 (contract+winning). The issue there is this season is basically a competition between Terry and Marcus. The player with the most impact on winning, in their respective roles, will be the one to stay. Thus far, Marcus has a lead on him, but it's not insurmountable if the salaries are in the same ballpark.