Again, from personal experience I have yet to ever get rid of a tool because it failed on me. The only reason I have ever lost a tool was through theft, the battery/charger/replaceable component was no longer supported, or the tool was too unsafe to use.

If I was a professional or ran a tool rental business I would 100% agree. But I wouldn't buy a pickup track no matter how durable if all I need it to do is grab groceries. It's better to get a tool engineered for the level of work expected.

for the typical level of work expected, or (as most Americans do with their vehicles) the "max" level of work expected?

There are plumbing tools I will never buy because I'm not a professional plumber. But you can be sure that the plumbing tools that I do own are top of the line for the tasks that they can accomplish.

What is the difference between "too unsafe to use" and "failed on me"?

Well, the one I am thinking of is an old-school all-metal belt sander that my grandfather gave to me.

The thing is an heirloom and may very well last forever, but basically has an unacceptable lack of modern safety features at this point. No trips, no guards, horrible ergonomics, weighs a ton, and has no grounding (keep in mind it's all metal). It also takes non-standard belts and I may or may not have cut my hand open twice just trying to change them.

So while I can understand the appeal of buying a tool that lasts forever, what are the odds you will actually want to use it forever?

Power tools: yes.

Non-power tools: not so much. My grandfather-in-law's thread cutters and pipe wrenches are every bit at the level of whatever I could buy today.

Ha, good example. I thought you meant unsafe from wearing out.