Hello the fire,
The main reason Adirondack Jack created the Cowboy Special was to make a lighter shooting black powder case to ease the recoil on his arthritic hands. That is why he didn't work at cutting any of the other cases down. He was also concerned about the wall thickness of the 45 Colt case as it gets thicker as it gets closer to the rim.
To those of you who are modifying cases and not having problems with fitting in chambers, good for you. Some did early on. Now it is just a personal choice to cut cases or buy them.