I think Arch has FOSS support kernel live patching Nixos also has an open issue where they seem to be discussing an implementation they might consider.

With upstream support and kpatch being FOSS I think the willingness is just low to maintain patches at a distro level and announcing it as a thing you can do yourself has limited audience.

I agree its super cool though and with containers and some of systems work for system level reboots and portable services I see a lot of potential for high uptime systems (like my laptop lol).