There is a responsibility for site owners to ensure the site is safe for it's users. But as to what lengths they go to it would seem it's very low, in theory they could ask for a certificate to show the caravan has been inspected and tested, but in real terms what seems to be the problem is keeping the camp site up to date rather than the caravans on it.
However no site really wants scruffy caravans on it, and the site rules can be used as an excuse to exclude caravans which don't look well kept, there are all sorts of other methods used, I know in Wales I have heard of sites being full to English speakers but being able to squeeze another Welsh speaker in. I would guess the same applies abroad, they may prefer German to English and do things to discourage the English. And if I am not Welcome then better to find another site.
It happens in many walks of life, you can't sack some one for their attitude to work, but you can look out for something to use to sack them, where if same thing done by some one who is helpful you turn a blind eye. If I was controlling a caravan site and some one arrives towing a caravan with a works truck I would wonder if he was a gypsy and if he would stop those with their expensive 4x4 and A1 caravan using my site, it really should not make a difference even if they are a gypsy, but I think I would be more strict on the rules with them, than some one with what looks like they care what they look like. Likely the gypsy has more ready cash and is more likely to spend it in my shop, however one still is likely to look for some reason to dissuade them.
I find the same caravan to tent, those using tents seem to be looked at as being a lower cast, in real terms there is no difference, but still there seems to be something which makes site owners look for the money spent on the vehicles and camping gear rather than what the people are like. Going with the family we have found we are not treated as well as my son, his caravan is better than ours, fact we own them both does not enter into it.