People don’t care, because people don’t know. RowHammer-vulnerable RAM is like canned food with botulinum and gasoline with lead. In 100 years, we’ll all be flabbergasted that everyone in the industry wasn’t arrested for letting it happen.
Do I want ECC, sure. Would bitflips ECC could prevent be in any in the top 10 reasons in year for file corruption, application crashes, and OS crashes etc... unlikely.
Track row activation counts for real, no estimates and no hash tables, and you're not vulnerable to this.
$50 more for the motherboard and $100 more for the RAM is not a "modest premium" for most of the desktop market. But aside from that, the bigger problem is that consumers (and especially gamers) will always prioritize the advantages that are more easily quantified. When forced to choose between ECC support and a few hundred MHz plus the option to overclock further, consumers will pick the faster processor.
If Intel offered a part at the high end of the product line that had both ECC and overclocking enabled, it would be guaranteed to sell quite a few units, because a lot of consumers will always want to own the top of the line part. And such a part would be an opportunity for a better experiment to determine how much premium users are willing to pay for ECC, if Intel also kept offering the current -K overclockable parts that don't have ECC.
It's not really a supported config, there's no guarantee it will work, no promise from AMD (other than it's not disabled), and you can't return a Ryzen CPU because the ECC doesn't work.
Various tests from various reddit posts show that some vendors "qualify" ECC dimms as working (an inserted Dimm increases ram available), some correct bits but don't correctly tell the kernel, and others actually do correct and report. So it's basically just a big mess. I'd buy an Epyc, but sadly unlike Intel the premium for a "server" chip is huge, if you can find them anywhere near MSRP. I looked for a Epyc 7313p near MRSP (announced in March 2021) without luck and finally gave up and bought a Ryzen.
With all that said, ASRock is from what I can tell the best AMD motherboard company to support ECC with AMD. I've got a ASRock X570D4U, other than it refusing to allow sharing a IPMI/BMC interface with the system, I'm pretty happy with it.
ECC is only officially supported on the Ryzen Threadripper PRO, and that's largely because it uses registered memory which will practically always have ECC capability.
Regular Ryzen PRO CPUs have the same ECC support as non-PRO Ryzen CPUs: functional, but not validated by AMD.
Ryzen PRO APUs have (non-validated) support for ECC, whereas non-PRO APUs don't support ECC at all.
So many people grumble, but I'm not really sure Intel should push ECC if desktops users aren't willing to pay a modest premium for it.
Many cheer AMD, which does not disable ECC on desktop chips, but neither do they promise ECC will actually work. It's a confusing mess between physical capacity (ram increases by 16GB when you add a 16GB dimm), and the actual correction of errors and telling the OS about the event. Only on the EPYC does AMD test and certify that ECC will work.