Interesting take on them being parasitical, I'd never looked at it that way. We joined one a couple of years ago, it seems they also take over municipal campsites and we stayed on some last year for 10-12 Euros per night. I'd always believed they we were willing to take over existing aires de campingcar and municipal sites that the Maires didn't want to keep open because of upkeep costs and poor revenue but the way you describe their business model throws some doubt on that.
We loved our caravans, the space and comfort were excellent but I hated the actual towing bit. I never felt completely in charge of the whole outfit, seemed like towing a large sail behind us!
One thing though, towing a caravan made me a better driver I'm sure particularly in the sense of being more aware of other traffic when anticipating making manoeuvres.