Write a couple of your own toy services as practice. Write a one-shot that fires at a particular time during boot, a normal service that would run a daemon and a mount service that fires after its dependencies are loaded (like, say, a bind mount that sets up a directory under /run/foo after the backing filesystem is mounted - I do this to make fast ext4 storage available in some parts of the VFS tree while using a btrfs filesystem for everything else.) You can also write file watcher services that fire after changes to a file or directory, I use one of those to mirror /boot/ to /.boot/ on another filesystem so it’s captured by my system snapshots.
I’d start by reading the docs so you have some ideas about what services can do, then you’ll find uses that you wouldn’t have thought of before.
Who could have possibly known? It’s almost as if the <35 demographic showed up to every election every time then policies they support may become a priority. Who could have thunk it?