I have never camped at a park that asked the age of my TT. Length and type yes, so they could reserve me in an appropriate sized site. Most of the campgrounds I have stayed at however only allow a 2 week stay unless you are seasonal. Some of them stipulate that you need to check out for a week before returning while others only state that you only have to change sites. I guess they are trying to discourage non-seasonal people from "living" at the campground or parking trailers that are nearly non-functional.
Indian Shores Campground and RV park in Wisconsin is a place I often stay. I see many new and old RVs. Some very old. I previously had a 1975 Aristocrat and there were RVs there that made mine look new. Some of them were restored and great looking while others were a little run down and faded.
Everyone camps within their budget and there are many that can't afford anything but an older "fixer-upper" but they still enjoy the hobby as much as anyone else. As long as the trailer can be pulled down the highway, I personally could not care any less how old other peoples trailers are. It's none of my business anyway.
It's not like a beat up, worn out '50s Shasta parked between two brand new trailers is going to lower their property values. I admire the people that own older trailers, either out of necessity or love, and enjoy seeing them being used.