Thanks for the explanation as I had no idea what hedging is.
It costs to hedge. If they are in it for the long run you don't worry about this.
Of course it costs money to hedge. It always costs money to hedge. All you've said is they shouldn't do it. You haven't bothered to explain why not.
If you assume the betting line is a good stand in for the actual probability of a game 7, then this is actually a very low cost way to hedge. There are unlimited examples of businesses engaging in equivalent hedging behaviors.