In industrial use (so not consumers) the main use for 3d printing is indeed rapid prototyping,

Sig Sauer and Walker Defense have both done some very cool things with mass-produced printed metal. Sig is, for instance, making silencers for their Spear rifles (at least the ones chambered in .277 Fury/6.8 x 51mm) that can't be done with traditional subtractive machining. Walker Defense makes a very unusual compensator that also couldn't be made with traditional machining; neither of those could readily be made through molding either. It's not cheap, but they're still mass-produced items. The surface finish isn't perfect, but it's pretty damn good.

These are both currently beyond the capabilities of home printers, since people don't generally have the ovens needed to sinter Inconel parts.