https://en.wikipedia.org/wiki/Systemd
... distributions have been forced to adopt it due to the dependency of various other software upon it, including, most notably, the GNOME 3 desktop environment.
... However, GNOME 3.8 introduced a compile-time choice between the logind and ConsoleKit API, the former being provided at the time only by systemd. Ubuntu provided a separate logind binary but systemd became a de facto dependency of GNOME for most Linux distributions, in particular since ConsoleKit is not actively maintained anymore and upstream recommends the use of systemd-logind instead.[58] The developers of Gentoo Linux also attempted to adapt these changes in OpenRC, but the implementation contained too many bugs, causing the distribution to mark systemd as a dependency of GNOME.[59][60]
GNOME has further integrated logind.[61] As of Mutter version 3.13.2, logind is a dependency for Wayland sessions.[62] ...