There are a few fundamental differences here.
One: the existing hardware isn’t lacking anything functional that the user requires. While it may be more secure implemented with TPM 2.0 its far from a hard requirement. After all bitlocker works on 10. The fact that you can presently work around it suggests the limitation is imposed from on high not a hardware requirement.
Two: The hardware isn’t all that old. General duty cycle on a phone is around 3 years, about 6 years on a PC. Apple has dropped support for 6 year old phones and 10 year old PC. Especially because intel continues to manufacturer a given CPU long after launch and OEMs continue to integrate them people are going to find machines that they bought new off the shelf within the last 3 years unsupported which unlike a 10 year old Mac feels like a rug pull.
VOLTE is a hard requirement. Continuing to support them would require entire installations all over the country to be repaired, maintained, and installed in support of hardware that was mostly 7-12 years old long past expected lifespan. It’s like the opposite of the Windows 11 thing.