That's uselessd. Software however relies on the other bits, e.g. logind dbus interfaces. For that there is a systemd-shim, but was not there initially and used to lag behind systemd for a 6+ months. Apparently it was also quite buggy. Seems ok now though.

To clarify, uselessd (http://uselessd.darknedgy.net/) is "a project to reduce systemd to a base initd, process supervisor and transactional dependency system, while minimizing intrusiveness and isolationism", not just the parent making a joke in the phrasing.