Multiple reasons, I know my breathing is affected and if that was the only reason I might have tried a pressurised mask, but with the hawks, the cost of feed, training, the nearest club I can compete in is at least 15 miles away...................its become a chore. After 45 years with the doos I just haven't a clue what I'm going to do, still get great pleasure from just watching them going in and out building their nests and generally enjoying themselves.