Many places, it would be impractical if not impossible
Camp grounds at the top of Kings canyon park in amongst the trees and curvy and hilly
You would have to bulldoze the whole campground trees and all, just to put in fewer larger flatter sites to accommodate larger RVs with toads and big fifth wheels
And they are frequently full all summer, why make it so less people can camp
Like was said those with RVs to large can camp outside and drive in with the toad, our 34 ft DP barely made it into the available spaces in kings canyon when we were there, I'm not sure this 36 Bounder would fit the same camp sites, i know a 40ft will not
Some Parks could be made to accommodate larger RVs, but i think in all cases it would mean fewer campsites,
I have nothing against choosing to have a larger RV, it's a matter of choice and finances,
But i don't think Nat Parks should be changed to the point that less people can attend and camp, to make room for larger RVs