Very true! I have had much difficulty explaining that horses can already do all the things we would like them to do when they are on their own – what we are trying to do is teach them what certain signals or words mean. Joe Joe absolutely refuses to take his left lead under saddle without a whole lot of fuss (he does have some physical issues that probably contribute to this), yet that is his preferred lead when he is free to choose. Selena will do a piaffe when she wants to trot out to the field and I want her to walk, but has no clue that I would like her to do this while I am sitting on her. It is my fault, not theirs. One of the things I feel is an issue is whether or how well the rider is balanced, which is why I keep suggesting that people drop their irons (and even eliminate the saddle entirely). If you can balance yourself without equipment, you stand a better chance of being properly balanced with it. No horse can do well with a rider whose weight is interfering with the natural movement of the horse. It is also easier (for me anyway) to feel what my horse is thinking when there is no saddle.
For myself, I find it difficult at times to explain to my horses that I would really like them to do this rather than that. Particularly when the wind is out of the north.
It is never the horse's fault