What Goin camping said.
Some units are more about camping and fellowship than about politics and pomp. 4CU has that reputation, and my unit (Heart of Texas Camping Unit) is rally-focused as well, we try to have a camping event every month.
You can also join any other unit's rally (space available, of course) as a member, and the courtesy parking thing is an interesting amenity we've never had occasion to use (we've only been members a little over a year.)
The actual red numbers are optional... there's no penalty for not having them in general, but at big rallies you have to display them somehow to help people identify different trailers in a sea of aluminum. Many people affix them to acrylic and hang them in the window during a big rally, etc. I was a member for a year before I put mine on, but I kinda like the way they look. As to your specific question about how the numbers are still down in the 4-digit range, when people leave the club their number isn't retired permanently, just set aside for some period and can be re-assigned. There are numbers much higher than mine out there, but I requested mine specifically because it matches my AIRForums number that I already had for some 4 years before even buying a trailer.
Il Carriaggio — 1975 Argosy 24 | Il Progetto — 1976 Argosy 28 Center Bath | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill