To answer your question, the actually purpose for that particular horses movement, is to pin in a western pleasure class. There is no "working" reason for it if that's what you mean. It's a pleasure horse trained to pleasure ride. It's not a ranch horse. Ranch horses (that are trained to show and work), however can ride just like that one.
But... if you were take a working ranch horse that was trained to work a ranch and not to ride in a ring, then it probably wouldn't give you a pretty picture like that.
Truthfully though, the hunt horses that race around the ring jumping really high fences... what is the purpose behind that?
The dressage horses that do all the fancy footwork, what is the purpose behind that?
You can pick apart any show breed because the truth is, when you enter the show arena, the "purpose" is just that, show.
That's my 2 cents anyway...
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