Just the simple fact that someone can’t plug in a hard drive and have it work every time, they have to go into a specific folder and write a specific arbitrary un-memorable UUID and tell it to always mount it on boot.

You can also mount partitions by label (LABEL=), but you have to name them yourself and make sure you don’t give two partitions the same name. The point of generating UUIDs is to have an extremely low risk of two partitions getting the same UUID generated.

But I think I get the issue, when I search for “linux automounting hard drive” I only see tutorials which explain how to use /etc/fstab.

It depends on what kind of automounting you are looking for, what they explain is the rare process of switching/adding internal drives that get mounted right after boot. First time that should be set up by the OS installer.

In case you were looking for automatically mounting USB drives/sticks, there are tools like udisks/udiskies who can do that and it’s possible they can handle internal drives too, but I never tried that since I want them to show up in specific places (~/Games, /var etc). Though I’d expect Gnome and KDE to have something like that included.