Nah, they were just a bigger hit with Hollywood, probably because horses and panoramic vistas are easier for the camera than skirmishes in the woods. Think King Philip, Tecumseh, Little Turtle, the Iroquois and the French and Indian War(s), the Creeks, the Miami, the Seminoles ... or Braddock, Harmer, and St. Clair. Just for starters. The Plains Indians were just a casual mop-up operation, aside from Custer's little mistake.
Excuse the off topic post. I just gotta stick up for my half of the country on some of these minor points ....