Originally Posted by its lbs not miles
Good thing the history of horse breeding the the US didn't follow that course or we wouldn't have any of the US gaited breeds we have today. If you check their ancestry you'll find non gaited breed bloodlines in the foundations of all of todays US gaited breeds. They have replaced most, if not all of the gaited breeds that were mixed with non gaited breeds used in developing them.
Actually a lot of the US gaited breeds that have non-gaited horses listed in their history stem because a gaited horse would occasionally pop up in the "non-gaited" breeds and so they used these horses to create a new gaited breed and/or expand the genetic diversity of an established breed. MFT is a perfect example of this as they used to allow any horse that exhibited the fox trot to be included in the breed. So there are a lot of non-gaited horse breeds listed in the history of the breed, but majority of the horses actually used in the MFT did naturally gait - they were atypical for their own breeds but were perfect for the new breed.
You also have to consider that when these earlier breeds were created - like the TWH - there was a huge niche that needed to be filled for plantations and easy riding horses that could go a long distance because horses were the main mode of transportation. They were in demand unlike today where horses are more recreation and a luxury than a necessity. So back then they could take risks to create a specific type of horse because someone could use the culls - even if it was hooking it to a plow or cart because it was otherwise too rough to ride - unlike in today's world where we have way too many horses for the homes available.
I see you mention old gaited breeds used to build the gaited breeds of today that have been replaced. Like who? TWHs used pacers mixed with trotters, not already naturally gaited breeds.
Different times require a different look at breeding practices. Thankfully we already have several gaited breeds of different builds, sizes, etc that most tastes should be met so why breed a gaited cross and take that risk.