I 3D print items that aren't mass produced, either because I'm one of few people who wants them so there's no market or I'm the only person who wants them because they're customized for me.
Most reasonable 3D printer users don't believe they'll replace mass production. They use them for parts you can't buy.
Once you get a 3d printer, you do tend to find many uses for them for things you could easily buy (organizing bins and the like) but I don't think anyone is buying them with this in mind.
I see it as the most important home maintenance tool. Saves hundreds per year on little things that break. Like a wall patch, small o-ring for a toy, drawer slide mount, basement light mount, etc. I will say though that the learning curve is a bit rough if you don’t have CAD experience.
