Because they win and challenge; chicken and egg.
Look, I'm not saying to sell VanPersie (although my personal opinion is that it doesn't matter), I'm saying that the club must not allow itself to be distracted by his contract situation. The fact is, we have alot of work to do in the next three months and it's all too convenient to let the VanPersie contract cloud other key decisions.
As I said, work out what we need to be a genuine contender, get it done and then Perse leaving means nothing and in the best case scenario, he signs as a cherry on top.
Put it this way, if tomorrow we announce Kagawa, M'vila, Vertonghen and Hazard (change the names as and how you please), the prospect of losing VanPersie becomes a whole lot less worrying.