its quite simple...unreliable flyers.
Say a busy saturday a flying clubs aircraft will be filled up using an internet booking system...particuarly with self flys wanting an aircraft for 4/5 hours to do an half hour trip to get lunch.
Then suddenly the morning comes...and half the bookings will disapear (even with CAVOK), because it is easy to cancel. If the customer has to ring someone to cancel they are less inclined to cancel, or wont book the aircraft for an off chance they will actually want to go flying
Hope this helps a little...
