ESR nailed this one:
"languages of particular importance to hackers include Perl and LISP" ... "LISP is worth learning for a different reason — the profound enlightenment experience you will have when you finally get it. That experience will make you a better programmer for the rest of your days, even if you never actually use LISP itself a lot."
I've never seen a Lisp programmer who couldn't very easily pick up any new language, though I've seen many, many programmers who specialized in every other imaginable language who had trouble learning new languages. There's something about Lisp that stretches one's brain. (I think it has to do with the circularity of defining something in itself.) Like a contortionist, nothing else seems like much of a stretch any more.
My college required all students to take courses in foreign languages and cultures, including non-western cultures. I'm amazed that we allowed people to graduate from the computer science school having only learned C++ and Java.
Yes, when hiring I rank this way above many of the other things here. Any Lisp programmer can learn "Source control, unit testing, and continuous integration" in almost no time, but a Java-only programmer who knows those 3 things may well struggle with closures, or parsers, or something that I actually need. If you know computer science and programming, we can teach you the processes, but not the other way around -- or at least, not on a timescale I'm willing to subsidize with payroll.