The vast majority of programmers never used or cared about Prolog.

They have missed out.

In terms of elegance, I've never written anything that surpasses Prolog.

For a defined subset of problems.

Most Portuguese universities had Prolog on their CS degrees in the 90's.

Also most companies HR departments will ignore CVs without an EE or CS degree from those same universities.

I studied prolog too! For a semester only but I loved it. I don't remember much of it but I loved it because it felt like a true "high level" programming language to me. Describe it a problem and ask questions. Felt like magic.

Also learning erlang was much easier when you had some basic idea of prolog. Clauses did not seem so weird and once you understood how clauses work you've basically got 80% of the language nailed.

What I don't really understand though is why erlang didn't go all the way. Why take only surface level features of prolog and ignore the really cool parts?

Erlang vaguely looks like Prolog, but it has semantically nothing in common with it. Even the syntax is quite different beyond base similarities to predicates.

I know, but if one has Prolog on his/her toolbox, Erlang becomes more approachable than knowing only Algol style languages.