I guess this should also be a question to ask anybody looking to buy a high end computer today: "Sir, before you buy this, please name two uses of this computer which cannot be done by a $400 PC."
PS: I am joking.
I'm still thinking about the first.
On the other hand I am always coming up with bent pieces of metal I really want.
With the conclusion that a sheet metal cutter would be far more useful than a 3d printer, so that is what I am going to get.
It's not just baubles, either, each thing improves my life somehow. To the holder of the falling toilet seat, to the toothbrush holder, to the sink sponge case.
And the argument of "couldn't you go to the store to get some of those things" is the same as saying "couldn't you go to the laundromat to wash your clothes"? Yes I could, but once you're used to the convenience and speed, you'll never go back.
Most of what I print are publicly available models, but some of them I did myself.
What I have done: shower head support, various boxes, curtain hooks, phone stand, drain filter, novelty dices, etc... Most of these I would never have thought of before I got my printer, and yet, these are actually useful stuff. For example, for the curtain hooks, before I had the 3D printer, I had to buy some that didn't quite fit because the original one that broke are not available anymore, and sometimes, they fell. The new ones I printed to measurements fit perfectly. That's the idea, you need something, you print it. Of course, there are many things you can't print or it makes no sense to, but it really is useful.
Also I originally underestimated PLA, it is actually quite strong. There are even ways of making it heat resistant (regular PLA starts to deform at around 60C, which can happen in a hot car).
That being said, it is still a hobby. 3D printers, especially the cheap ones are far from consumer friendly and you need to be familiar with its workings and how to setup your slicer. And there is the big one: CAD. You can limit yourself to printing others people models, but you would be missing on a lot of potential.