It has something to do with a new contract.
For the past couple of months, I've been hearing from team sources that Jones-Drew has been talking about a new deal. He has two years left on a contract he signed in 2009, but that deal makes him the eighth-highest paid running back in the league and he was the NFL's top rusher last season.
So you can see his point. But you can also understand why the team would balk. Jones-Drew is entering his seventh season, but he's only been the primary rusher the past three. He isn't a big guy, and while he takes great care of his body, the wearing-down factor has to be a concern.