I'm not disagreeing on that count. In Europe, their RV parks have a large, stainless steel trough for people to drag their cassette toilets to, empty them, and rinse them out. Here in the US, it is doable, but nowhere near as convenient.
I personally prefer the US style black tank setup for my way of doing things (because as above, I can easily go to a CG, SP, or even a truck stop, and empty the tanks.)
There are some cool European floorplans that should translate to the US, though. Black tanks are not impossible to engineer around.