super singles

Several possible reasons.
1.Cost. Until the builder puts them on a rig add in the cost of the rims in addition to the tires if an owner wants to make the switch.
2. Availability. There might be some concern on wide spread availability beyond the interstate corridors should you have a failure.
3. Consumer demand. The builders probably won't add them as anything more than an option until we the buyers start demanding them.
4. Fear of the unknown. Duals have worked pretty well for a very long time. Why switch?

Super Singles (Wide Base) tires are used by trucking companies primarily for weight savings. Two tires and two wheels less per axel equates into saving of approximately 200 to 400lbs per axel. Additionally, a fuel savings of .25% to .50% mpg and a smoother ride is a benefit. One downside of Wide Base tires is availability in remote areas. (Becoming less of a problem as production increases and more dealers stock the tires.) Also the ability to “limp to the next exit” with a flat tire may be a concern.

changing demographics would be my guess. I belong to a lot of RV lists and forums and see many posts from single RVers. if there wasn't a market or at least a perceived market you wouldn't see them. the question is...will the "super single" go the way of the spiral staircase leading to a roof-top lounge and fizzle or will it find its way into the mainstream?