Horses buck for various reasons but bucking is a dangerous habit that should be halted as quickly as possible. There are horses that never buck when ridden but this doesn’t mean that they can’t, they simply don’t do it. Others may buck once or twice when you first get on their back and then they just calm down and go on with the training process.
There are other horses that keep on bucking in training but they stop it after several times because they see that you won’t quit training even though they react that way. There are cases when the horse gets accustomed to bucking and throws the rider off and when the horse does this he sees he is a little bit in control over the rider and he just considers this to be an evasive tactic.
But these aren’t always the cases when a horse bucks because a horse can buck even when he is in pain or something irritates him. Sometimes when we are riding, we just give mixed signals confusing the horse and the horse has no other way out but to buck. Sometimes, we, riders, can bring it on. Watch the funny video of some bucking horses throwing off their riders.
https://www.facebook.com/schumacher.fenomeno/videos/229837681241066/