Remember the Paul Graham essays Great Hackers & The Python Paradox. To quote an paragraph for those too busy to read those two:
But when you choose a language, you're also choosing a community. The programmers you'll be able to hire to work on a Java project won't be as smart as the ones you could get to work on a project written in Python. Great Hackers
In a recent talk I said something that upset a lot of people: that you could get smarter programmers to work on a Python project than you could to work on a Java project.
I didn't mean by this that Java programmers are dumb. I meant that Python programmers are smart. It's a lot of work to learn a new programming language. And people don't learn Python because it will get them a job; they learn it because they genuinely like to program and aren't satisfied with the languages they already know. The Python Paradox
How that translates into recruiter talk. Just imagine that you need to fill a position for some boring mainstream language. After few days (or weeks, months, quartiles) of interviewing cram school students you're exhausted with candidates who fail your variation of a FizzBuzz test so you need a way to drastically improve quality ratio of your applicants or your head is going to explode very soon. The solution is very simple just add some esoteric language to weed out resumes and hurray you'll have much smaller stack to sort.
Why this works?
Majority coders took programming as a job, something you do for money so you could spend those money on things that you need and things that interests you. If there was another job requiring same effort and payed more most coders would be doing that instead. I mean why would somebody be reading about tower of Hanoi when there is a good game on TV? If average coder needs something to advance their career so (s)he could make more money so (s)he could buy bigger TV they will learn it, it doesn't matter to them. It's the people who see programming as more than work who are complaining. Just imagine if there is enormous demand for violin players, it pays good money and work is easy to find. So if you aren't 100% tone deaf you might say : I can't find programming job, at least not one that pays well, so here's a good career choice for me, in the end everybody has to earn their bread somehow. So you buy the book learn violin playing in 24 hours and maybe get certified. Afterward you're doing your job and get payed, than your colleague is asking you do know to play Niccolo Paganini Fifth Caprice. Shit man we only do pop music here,what the hell do you need those kind of crap for? So you continue playing vanilla pop
at work and program at home why the bozo practices Fifth Caprice. (*)
So whenever I see job posts of niche languages mingled with mainstream languages I'm asking myself how much of the niche language the person is going to work with, if at all, or this is just a recruiter dirty trick to improve signal to noise ratio.
And if you think that I'm just fooling around you could see this technique mentioned in The Passionate Programmer chapter 5 where Chad Fowler uses Smalltalk to find out Java programmers in India.
Everybody could be taught how to paint, Michelangelo must be taught not to(**)
(*) This part is slightly edited post from, comp.lang.lisp original is found here
(**) I don't know where this quote is from , I think its pg but I can't find the reference.