Because I firmly believe the gain or loss in market value is completely separate from the operating profits.
Gain or loss on market value belongs to the owners. That's part of the incentive to buy a sports team in the first place. Capital gains are given preferential tax treatment based on this very principle. You have to encourage investment because of the risks that are entailed. Like them or not, we need rich people to invest.
And as you said, players are not going to kick in anything if the market value goes down.
It's an amazing thing that the team values continue to rise. It can't go on forever, I don't think. s*** does happen, eventually, it's inevitable.