Those cartridges were developed when the companies making the guns for them wanted to have cartridges people would buy to shoot in them. They developed cartridges that worked in any of the guns, but named them in such a way that people would believe they were somehow different from each other. The companies made a lot of money from the cartridges they sold under their own names. Merwin Hulbert also made a .38 cartridge that is identical to the Colt and S&W cartridges, and some Spanish companies did the same. It's all marketing, like calling the cartridge a ".38" when the diameter of the bullet was really the same as that of the old .36-caliber ball fired in the percussion guns that the companies were trying to replace with cartridge guns in people's minds. Marketing.
