In yellowstone, the "no tents" (no canvas) camping area is because of the presence of bears.
In other parks, (eg Yosemite) tents only require a short walk from the parking lot to the campsite. No vehicle camping in the small, dense parking lot.
In Zion, I spoke with the gatekeeper of a tents only campground. It was a matter of environmental impact and camping equity. At this one, he had a placard of vehicle profiles that were not allowed, tent or no tent, including trucks with TCs, vans and other custom RVs. Basically, if it has propane, plumbed water, a heater or a refrigerator (easily seen from the outside) it is not allowed in tents only parking.
I have not encountered RV camping that restricted pop ups (except Yellowstone).
