Carrying along from before, one of the biggest things that bugs me is the canard that everyone born before Henry Ford was a horse-rider. Everyone could just jump on the back of the flightiest, most unpredictable animal (except for the fact that they are predictably unpredictable) and ride like the wind at will.
Not a chance.
Horses, unless they are those sad, old, beaten-down lifeless trail ride horses for children and tourists, can, and will, throw you off. If you climb up onto even a quiet school horse, you will inevitably have an unplanned, un-co-ordinated dismount, possibly with broken bones. Those tourist trail horses will not take off just because you want to, either. They are "safe" for a reason.
It takes practice and training to be able to ride a relatively quiet horse relatively well. Until the middle of the 19th Century, that excluded about 95% of the population, simply because horses were an expensive status symbol.
While horses were more common, they were usually draught horses, typically used to pull wagons and carriages. Ostlers were tradesmen, but they weren't usually accomplished riders and even today, not everyone who works around horses knows how to ride them. It's a peculiarity of 19th Century North America that has the bulk of the farm population learning to ride, but even then, they were riding quiet draught horses, not spirited chargers. Most people, in most of the world, had bullocks doing their ploughing and haulage.
That's why watching TV shows or movies where anyone just jumps on a horse and takes off, even though they have not shown any history of being around a horse (like the character of Ragnar Lothbrook in Vikings, for one), always jars me. True, almost everyone in the early 21st Century North America can drive a motor car, but I rather wish the romanticist writers and entertainment types treated horses like motorcycles. We know full well that not everyone knows how to ride a motorcycle. TV shows don't have the average character just grabbing one and going; they grab a car or truck instead, if they need to. But somehow, in 'historical' pre-motor-car settings, everyone is just born knowing how to ride a horse.