I don’t know the exact year, but drastic criminal punishment sharply declined during the Enlightenment. A good source for how things changed after the start of the Enlightenment is Steven Pinker’s book, The Better Angels of Our Nature.

When automobiles became abundant.

Also, in about 1900, the last of the Indian wars (Apache) in the old west ended.
”...the unwritten law of the Western plains measured horse theft severely because it could leave a man afoot in hostile country.” -from Time-Life Books, THE OLD WEST, The Cowboys, page 214.

It’s still a pretty big crime here, class C Felony. But I’m in cattle country so we see it a lot. Up to $25k per animal.

Not from Texas, are you? : ) And any Westerner who would attempt to commit a crime in N. Korea is just asking for trouble. Might as well travel to some heavily traditional Islamic country and violate one of their taboos.

The horse was transportation, business partner, friend. It was not always all of those, but always at least one of those.
As cities became more established west of Ohio, and beyond the Mississippi, fewer people needed horses. The invention of tractors made a huge difference. This didn’t eliminate use of horses on farms, but it sure made a big dent. My guess is, it was around that time. Horses would have been demoted in esteem by then. Race horses are an investment, so monetary value was of more consequence than emotional attachment.