With the emphasis on the "motoring". Touring is a very weight conscious activity, at least loaded is. You carry more capability than in virtually any other wheeled sport, but with extreme weight limits. Nearest thing would be RVs, and even they do not have the versatility of terrain, and camping place that a touring cyclist has. Most power vehicles do not have the wheel issues. There are trade-offs and I don't think there is any experienced touring cyclist who thinks that discs aren't the right choice at times.

I'd buy Hdyro discs a lot faster than most other road sports would, if they were priced in line with hydro disc on MTBs, unfortunately they are very expensive. But at least most tourists don't use brifters so getting all the pieces to work together, or be at a reasonable cost, is not a big issue for tourists.