How come some of the core Linux projects are missing maintainers?

I was playing around with my fingerprint reader today and landed on [linux-pam/linux-pam (#301)\](https://github.com/linux-pam/linux-pam/issues/301), where you can read that proper implementation of \\`any\\` directive is impossible simply due to missing manpower.

How come such a core project as PAM is missing manpower? Most of the big distros (if not all) are using PAM and the man behind it doesn't have enough time for it. Does he even have time to address new vulnerabilities popping up? Why is it even a single man operation? What are the distros planning to do when he's not capable of maintaining it anymore?

It seems so weird that something so core to modern Linux is left by itself to wither.

https://redd.it/1tdrfnj
@r_linux