Are you sure they don’t get sent to Apple as part of some telemetry / diagnostics implementation?

You don't need them to be sent to Apple. And if errors in console get sent to Apple, it's surely filtered through a heavy suppression list. You can open the Errors and Faults view in Console on any Mac and see many errors and faults every second.

They could start attacking those common errors first, so that a typical Mac system has no regular errors or faults showing up. Then, you could start looking at errors which show up on weirdly configured end user systems, when you've gotten rid of all the noise.

But as long as every system produces tens of thousands of errors and faults every day, it's clear that nobody cares about fixing any of that.

Oh they absolutely are. But Apple clearly doesn’t care enough to actually fix them. They seem to get worse every release.