I'm happy that you care enough to ask this question, many people, not in the business, don't even think of the welfare of the horse. The shifting of weight from one hind leg to another is the method that horses relax and rest. The situation regarding hard surfaces: It's actually much easier for a horse to pull a carriage on a hard surface than a soft one, heck, I could pull one on a hard surface. Most city permits depend on having healthy, well cared for horses, with include proper shoeing, nutrition and grooming. Horses are vet inspected on a regular basis and those results must be submitted to the branch of local goverment that is in charge of the operating permits. The carriages themselves are inspected as well, plus the drivers are required to have driver's permits. I'm not saying that there aren't exceptions to the rule, of course there are. Some people just don't see horses or any animals in any other way other than how much they can make with them, but in my experience, they are in the minority, thank goodness!