For me...classic design + classic cartridge = 8)
Seriously, with that route of thought, we'd have 2 or 3 chamberings and that's it right? Why have a .30-30 when you can have an .30-06? Why have a .30-06 when you can have a .300 WM? Why have a .300 WM when you can have a .375H&H? It goes on and on and on... There's a lot more to enjoying a cartridge and firearm combo than "superior ballistics". It would be like asking why have a .44 special when you could have a .44 magnum? It's one of those things you either understand or you don't.