You're quite wrong.

You can, in fact, print perfectly well in any thermoplastic, including PVC (although it's unpopular due to toxic fumes). Nor is strength neccessarily an issue. In fact you can 3D print polycarbonate parts strong enough to scratch-build a drone - props and all.

No - the reason you wouldn't want to print parts for your kitchen sink isn't because you can't, it's because you rarely need such parts, and when you do you can simply buy off the shelf parts for next to nothing. A printer simply does not justify its overhead for most people. It's like having a lathe: useful if you're seriously into manufacturing or crafting, but not worth it if you want something pre-designed. There's just not much that it wouldn't be easier to just buy.

How much is a 3D printer that can print durable thermoplastics that I can use for replacement of trivial household items? I thought that would require an industrial setup to do. If you're telling me that I can just start replacing plastic crap in my house, including critical parts like plumbing, with a 3D printer that can sit in its own corner, I probably WILL buy a 3D printer.

A Bambu Lab P1S is $600, and then you gotta buy PET-CF filament, and there's shipping consider as well, so let's say ballpark $800 to start. They make more expensive printers too if you have the budget for it, but the underlying technology is mostly the same. Filament comes in 1kg rolls, and small stuff is like 50 grams, but a large piece of pipe including support structure could be as much as 500g, so if you end up printing a large amount of large items, eg https://makerworld.com/models/1441653 instead of https://makerworld.com/models/77668, which is 2g, and cheaper PLA, filament costs are going to add up.

https://bambulab.com/en-us/filament/collections/functional-p... goes through the various filaments and their different strengths and weakness, depending on the kitchen sink drain pipe you're printing.

> They would if you could print things out of durable materials that had weight and structure

You and I totally would, but we're nerds!

Think of how much coaxing it takes to get the average North American homeowner to replace a leaky shower head or a spark plug. A lot of normal happy folks will spend their lives not really learning to fix things much, and that's quite alright, IMO. We don't all need to be good at everything.

I actually printed a few PETG ones. They are nigh indestructable compared to PVC.

As noted above, it's the mechanical design / CAD that has to be seriously learned to do anything useful.