Comment 3 for bug 1325309

suspend and NM only indirectly require it. logind does the management of user sessions, tracking of "foreground" sessions, dynamic ACLs etc. these days, and logind requires cgroups. NM, power management, device ACLs etc. all use logind's functionality.

In other words, cgroup support is pretty much a "must" these days. Not only for logind, but also for LXC and other things.