I think it’s just a shortcut because of lack of experience with systemd (this is not intended to be offensive btw - if cron is already installed and you save time by just using what you know, why not?). I would be very surprised if cron could do something that can’t be done with systemd timers.
Systemd can be very powerful and you can even depend on individual devices being added/removed. I’m pretty sure you can even replace the udev rules with a systemd equivalent if you tried hard enough.
