And when they get more experienced, they'll probably want to migrate that site to a new host (for example my site was bbkane.github.io before I moved it to bbkane.com), which will break absolute links to the first (now down) domain. Yes, best practice is to set up a redirect from old to new anyway, but that's the kind of thing someone doing this for the first time doesn't think about.

So there's definitely a case for beginners using relative links. And it's less repetitive to type!