No, it stems from poor conformation. If you look at the shoulder angles on some of these halter horses today they are pretty straight, thus the horse tends to be straight through the pasterns, in addition to the pastern being short. Straight closed shoulder leads to no reach in the front. In the hind end, the pelvis is usually too short and flat, the femur too long, the patella kicked back and not aligned with the SI, the tibia too short, and the cannons to long; thus they can't track up past their stifles very well. Those are the trends today. A lot of halter people like that modern breedy look with hocks too straight, a mile off the ground, straight shoulders, and a really high neck set. I prefer to ride my halter horses so I tend to trend the opposite direction. When I strip this horse's weight down, he looks like a racehorse. I'm not saying he's fat at all, because in reality, he's not. You can feel every single rib easily... I usually strip him all the way down and get him really lean after show season and then build him back up.
But then again... I do things a lot differently than most halter people do. I turn mine out (obviously), I ride them, I use a complete feed and good alfalfa with no supplements, and I give them a job.