ConsoleKit was a Gnome project which was abandoned when they decided to switch to logind. There was actually a fork of it called ConsoleKit2 for a few years but because everyone had to support logind anyway in order to support Gnome and systemd it was a second-class citizen that slowly died out. The distros shipped systemd+logind as default because that was the only option Gnome supported, and the other desktop environments did their testing with logind and let the ConsoleKit2 code bitrot because that's what all the distros used, and gradually it became less and less usable.