I have a theory. Been unable to attend games since New Year because of a serious arm brake and fractured neck. So not been able to go to games and placed my 2 season cards on the exchange for every home game since. Very surprised when the first game I used the exchange for I received confirmation within 30 minutes that the seats had been sold. Thought it was a fluke but same thing happened for each game. I came to the conclusion that the hospitality department was grabbing them. Put the derby tickets on 2 days ago and so far nothing. I believe the club has decided not to allow tickets to be sold on even through its own internet function in case united supporters are prepared to pay for hospitality just to get tickets.