There are plenty of low-budget casual customers interested in those machines, either gotten as a gift from relatives/friends, or bought second-hand in refurbished stores, and in both cases the machines are pre-upgraded from their previous owners.
Their use should be encouraged, both for ecological purposes, and because prosumer PCs from 2012 are much nicer machines than $200 2022 laptops anyway.
I, for one, could probably take care of my daily workflow with a 15" 2012 rMBP, if it still received security updates.
Not as smoothly as I do with my M1 Pro, but work would still get done.
Apple is dropping support for those machines for greed, plain and simple. Even if they couldn't receive the latest OS version, security patches should always be provided.
Food for thought: on YouTube you can find videos of an iMac G3 running OpenBSD, latest version from 2021 (!!!!!), and being safely connected to the Internet, with the same level of security patches compared to a modern PC. Also not completely unusable for light websites.
Sure, it's an extreme example, but there is no reason to trash old hardware that can be repurposed, even if it is for niche use-cases.
Imagine if Apple released a bootable OS for those machines, enabling old Macs to even browse only one Safari tab at a time and nothing else.
There would be a lot less waste around, that's for sure.
Actually it appears that Google is doing kind of the same thing with ChromeOS Flex (not for PPC Macs though).