I think it's also a bit of a testing ground for the main repos as well. I maintained the `ruby-build` AUR package for a couple of years after the previous maintainer wanted to step down, but they eventually added it to the main repos and now it's maintained by one of the official people. (I don't recall ever having to do more than paste in the new release tag into the PKGBUILD each time and then generate the new .SRCINFO and checksums in terms of actual maintenance, although I'd test locally first before pushing of course).