Many more people try to ride a uni than ever succeed. Many physical activities are not as hard as they look. Unicycling is not one of them.
On the first several attempts the phrase "impossibly difficult" repeatedly comes to mind. There are just so many things to get right at once.
On average it takes about fifteen hours of practice to get going. Most people hurt themselves long before they get that far. It takes real commitment to keep trying but most people can do it if they keep at it.
The early things to learn are how to get off and the judgement of when to do so before it is too late. Unfortunately, at first, that time window is only a fraction of a second after you take off.
It is quite surreal when it finally happens. It gets easier once the balance reflex kicks in.