I think a big part of the problem lies with ammo manufacturers using so many different naming conventions for the exact same cartridge. Why do we need 9x19, 9mm Luger, 9mm Parabellum, 9mm Nato, 9MM Para, 9mm Service Grade, etc? How does someone new to guns know to differentiate that from 9mm Kurz, 9mm Corto, 9mm short, .380 ACP (which is completely different from 38 ACP), .380, or 9mm Browning among other designations. For something as important as this, it should be made as easy as possible.
When you go to the store and look at 12 ammo options all having different names how is the consumer supposed to know which one falls under 9x19 vs 380 ACP. It's easy to criticize "dumb" consumers but gun store clerks can be just as bad.