For the carriage horses, I think they have to be ridden because there is no driver. I saw the same thing too and thought why are these men riding the horses, then I noticed the open carriages did not have a driver. When they showed photos of the Queen and Prince William from their eye view they were looking directly at the horses back end. I too noticed how fidgety some of the horses were. The one black one next to the Cambridges tossing it's head at almost every stride. And I also noticed at one point one of the carriage horse riders tapping the horse next to him with a crop when it started acting up and immediately it settled. Beautiful horses and tack. I'll admit I kept getting distracted toward the horses and found myself watching them more than the bride and groom.