The bulk of CVEs that crossed my desk in the last couple of years were in things that wouldn’t matter on a 32-bit system, like problems in brand new graphics cards or fibre channel or 10G Ethernet, or KVM hosting, or things like that. There wasn’t a huge flood of things affecting older, single-user type systems.
But in any case, I’m sure Red Hat etc would be happy to sell backports of relevant fixes.
It’s not that I’m unsympathetic to people with older systems. I get it. I’ve got old hardware floating around that I’ve successfully kept my wife from ecycling. It’s that I’m also sympathetic to the kernel devs who only have so many hours, and don’t want to use them supporting ancient systems that aren’t still widely used.