I think it's because of the booking deposit that the C&CC sites have spaces. I can't understand what the problem is with paying deposits, it's not as if you don't get your money back! I suppose it's the case of, if you don't pay a deposit you then don't need to bother to phone to cancel, should you need to. Fortunately, thats the exception rather than the norm.
I have just booked four CC sites for our hols and haven't parted with a penny in deposits. I think the CC should go back to charging as it could deter some of the "no shows" :O)