Another factor may be the way many sale babies are raised - instead of growing up out in the pasture with their peers, they are mollycoddled, hot-housed, and fattened up like halter horses. Which would be fine, if they were going to
be halter horses, but it hardly prepares a body for more athletic pursuts. Development-wise, hand-walking and treadmilling is no substitute for romping over natural terrain.
I worked in sale prep for a while, and those particular kids spent more time in the wash stall than in the turn out. Fed to the gills, paddocked out of one anothers' sight so they wouldn't 'play too rough' or race each other...they were ready to explode by sale time, but they sure did look pretty.
