Most people who had horses also seem to have let their servants ride them. There's one bit in the book we just read, where the Rev. Holland writes in his diary that his servant Robert has taken out the "great horse" and ridden it on an errand rather than walking, and that he will "rot with laziness"- obviously, the reverans didn't really approve of this! I presume that the "great horse" would be a heavy horse- used for carriage work and/or ploughing as well as being ridden. In P&P Jane Bennet cannot have the carriage because the horses are needed on the farm.

One of the results of the long, protracted war with France was that the government encouraged the ploughing up of pastureland for growing crops by publishing leaflets promoting it, and also doscouraged the excessive ownership of horses by taxing both them and carriages , so by the time of Emma, ther was a definite tendancy to own less horses. This particuar fact, and Mr Knightly's preference for walking, is expanded in Mavis Batey's Jane Austen and the English Landscspe amongst other places.

I think you've also got to take into consideration the personalities involved. Today, many people, especially women, don't particularly like driving and maintaining cars, even if they can affford to. So it is with horses- I think you tend to either love riding or not like it at all, in which case you'll either do it at every opportunity of avoid it like the plague.