<p>Have people been using 3D printing to genuinely create a number of needed objects in their homes, and if so, what? Or is 3D printing better for special niche interests like art projects, home engineering projects, etc?</p>

Both.
3D printing is especially useful for creating replacement parts for things for which it would otherwise be difficult, expensive, or impossible to obtain a conventionally manufactured one. You may have seen in the news recently the
story about 3D printing being used to replace hospital ventilator valves
that were not available in time to save patients who needed them, and that normally cost \$11000 from the manufacturer. But the same kind of thing applies to regular household items too. For example, I've replaced broken wheels on my child's toy cars, a broken windshield washer fluid coupling in my car, and various similar things. I'm also planning to replace broken plastic wheel bearings in my vacuum cleaner (the manufacturer's design was atrociously bad and I'll probably adapt it to use real bearings with a 3D printed adapter), a window switch in my car, and lots of other things I can't remember at the moment.
Of course you can do craft and hobby things too. I don't think this really calls for examples/evidence.