Dangerous on both ends-Rough in the middle

There are Long-riders and Short-riders, long-legged eventers and adventure striders... we've browsed and bred horses for any imagineable desire, specifically conformed for the task.
Can a mustang jump, does he have cow-sense, are his feet right to run endurance. Can he do dressage, pull a cart and work at liberty. The answer is YES, " born with what's needed" a friend once said and Will James called his mustang "Big enough". The answer is YES, Yes yes... so,  why do we breed, if nature provides us with the genetics and free upbringing of a sustainable versatile and very trainable horse, that indeed often is a natural ambler and most comfortable..