Really just depends. I don't have one in my p'up, nor do I want one; there are other options. I have never liked the idea of my bathroom being in my bedroom.
I most often boondock with my pop up, which means no campground...no facilities...toilettes, showers....no anything other than what I bring with me. For bathroom issues, I use the "luggable loo" (google it) for the big jobs and the thirstiest looking tree I can find for small ones. I just put the luggable loo behind a bush or something; I have a small shower tent I use if I'm in a more exposed area.
For my purposes, an outdoor shower comes in more handy than the indoor variety. The indoor ones make quite a mess...I can just take a quick rinse with the outdoor shower head and call it good.
If I do happen to be at a CG, it's a forest service CG and they have vaulted toilettes...so I use them and the luggable loo stays stowed away. Then there's the occasional state park and national park CG which also have facilities...so I don't bother with the luggable loo on those trips either.
