Are you talking about servers? Because it's not 2000 anymore; the idea of servers running single instances of Linux for months or years at a time and rebooting is so infrequent that an extra second or two is no big deal, is obsolete. The cloud is king, and in the cloud you want to have instances which can be started up and shut down quickly and safely. That means that systemd makes just as much sense on servers as it does on desktop and mobile systems, if not more.