In the course of a typical week it would be interesting to know how many people either "no show" or cancel late because the cat is sick or "traffic delay" (real or not - and is the the provider's problem anyway?). The thing is that from day to day it is impossible to predict. If the provider concerned is expected to just take this on the chin then it means either higher charges all round or tightly scheduled bookings, resulting in delays some of the time. Would punters be prepared to accept no-refund deposits as an alternative? In practice I suspect many providers have an informal system - accept it the first time and, maybe, a caution if it recurs. This seems very reasonable to me. And, as Slim has said, emergencies and unpredictable matters arise and must be dealt with.