The old way has literally no way to differentiate between a frozen process and one that just simply wants to keep on running after the session's end, e.g. tmux, screen.
It's trivial to run these as a user service, which can linger afterwards. Also, systemd has a configurable wait time before it kills a process (the "dreaded" 2 mins timer is usually something similar)
which was fine for everything that didn't need a watchdog. systemd on the other hand still lacks most common usecase and people bend over backwards to implement them with what's available. ask distro maintainers who know the difference between the main types of service files...
It's trivial to run these as a user service, which can linger afterwards. Also, systemd has a configurable wait time before it kills a process (the "dreaded" 2 mins timer is usually something similar)