To me there's not so much difference. Also, racing can be fun. Also, this kind of distinction does seem a bit not so relevant.

UL backpacking has taken off like wildfire, with people doing 50 mile days, days on end. People going for personal records and records on the big trails or just for distance. Is it a race? Is it fun? Who knows. No need to travel abroad. It can even be thrifty. People are also doing this in mtbiking. It just seems a bit overly quiet on the road side of things.

Now, there is a fairly active email list out there. People ARE getting into it and going UL on the road. I just haven't heard much about big distance pushes. I think the saying is that "less than 12 lbs including racks" is UL. But the concept usually avoids racks.

Maybe Lon is right and it's safer to get a bit delirious out on a trail and that being fatigued on pavement is a bad idea.

Another angle is that the Tour Divide race IS a "road tour/race." I've read that only 5-10% of the 2750 miles is on trails, the rest is on dirt/gravel roads.