Is this also true for Utah? IMO, Southeast Utah has some of the most amazing scenery in the US. I would bet that once you see it you will want to do more than a quick drive-through. I see that you are already planning to drive through Moab; I would recommend spending at least one full day there. It is close to Arches and Canyonlands National Parks and full services are available in town. It will be crowded that time of year (weekends especially), so be sure to make reservations if you go.

If you are campers, the San Raphael Swell area (the area along I-70 and W of US 191) is very beautiful, but there are no services whatsoever. You would be living out of your car / tent / RV while there. Towns are few and far between and you'll be hard pressed to find even a McDonald's when you do go into town. It is as close to a backcounty experience as you can have in your car. It is definitely worth it, though.

I presume you are already familiar with Monument Valley and Mesa Verde. If not, those are also worth looking into.