Personally, I think the issue goes back to your first few RV's. Our first RV was a truck camper and then a Class C. On both the bathroom was an all in one and was small. When you buy that first big coach, your first must have is a larger bathroom. That usually included a split bath where the salesman showed you all that walk around room between the shower and the bath. I would guess the majority of the late 90's through 2005 RV's came with the split bath.
Now people want more and are demanding the rear bath with all the room. Our last DP was a side aisle with an all in one bath. We loved it. It was private, large and felt like we were at home.
If you're looking at a larger RV, give the all in one or side aisle bathrooms a chance. They're not like the old bathrooms you had in your first coach.