Yeah I know it's because of TPM. But presumably at some point computer manufacturers added TPM to their motherboard/CPUs to be able to say they have or can upgrade to Windows 11.

Not saying there's a definite time cutoff, just generally speaking it seems like somewhere around there more computers started including the TPM capabilities.

Still three years isn't that long. I'd hate to have to trash my motherboard and/or CPU just to get security updates.