My opinion is that is just snobbish.  There are perfectly fine rigs and perfectly fine people in RV's that are well more than 10 years old.  Not everybody has nor wants to put a lot of money into a coach.  Some folks go on 1 to 2 trips a year tops.
My Toyota class c is well over 10 years, but the Bounder we have is only 7 years.  If I went to a place that excluded older coaches, I would leave and tell them why.  It's ridiculous in my opinion.  However it's their place - their rules... But my free choice to not trade with them.