I think it's a bit odd too.
I got my van as a move up from a small trailer. I found the trailer I could take almost anywhere, but it was not very comfortable and a huge hassle most of the time. The van is a whole lot easier to deal with. But the style of traveling is different - you really need to be moving around for it to make sense. Parking for days on end and then needing to run into town for something can be a hassle.
If it's a matter of having extra space when you are carrying grandkids a long on some trips, I'd just pack a tent for them. They'll think it's fun, and you don't need to worry about the sleeping space.