It’s amazing how £25 doesn’t sound much when it’s not your money, but think of this. An average season is about 235 nights and there are around 200 sites in network. So to spin it around, if this happened just once per night, every night, across every site then £25x235x200 equals £1,175,000. That suddenly sounds like quite a lot.The three pitches weren't available as the site didn't know that the people weren't going to turn up. So it wouldn't have helped you. We don't know why the three parties didn't turn up and one or more have them may well have intended to get there but didn't make it for valid reasons - Covid, breakdown, illness etc.
The loss to the Club is pretty small. There are 95 pitches. At say £31.50 per night (pitch + 2 adults) that's total takings on 92 pitches of £2900 for one night. If deposits were £25 (as per CCC) then they might have recovered £75. Return one or two for valid reasons and you could be looking at £25. It doesn't sound to me like such a small amount would justify the change to taking deposits. Any additional income would be very quickly swallowed up in additional Admin costs. So I think your example actually demonstrates why deposits are not worthwhile.