systemd is usually a root process, regular user does not control it. Whether user being logged off means no such user processes should run is a policy question

systemd is usually a root process, regular user does not control it. Whether user being logged off means no such user processes should run is a policy question that has different answer on different systems and depends on the user as well. Systemd "unified solution" - killing user processes on logout - is not working well for many people especially on shared machines.