Unless they're assuming it's exploitable on Apple Silicon as well, or are being extra careful just in case.
Things like OpenCore Legacy Patcher prove it's possible; they just don't want to.
I don't think anyone feels entitled to new features in perpetuity. Security updates only would be fine thank you.
Don't tell me the richest company in the world can't pay for a couple of developers who just want to rest and vest to take care of and test the legacy platforms. A cushy job and you keep the customers happy.
Ironically the best way to stay safe on these computers is to install Windows or Linux.
1. All hardware and software should come with a highly visible end of support date.
2. All hardware and software should notify people when it is no longer receiving security patches. It should also explain to users why running unpatched software or hardware is dangerous.