Functional Programming For The Rest of Us

So what is FP? How did it come about? Is it edible? If it's as useful as its advocates claim, why isn't it being used more often in the industry? Why is it that only people with PhDs tend to use it? Most importantly, why is it so damn hard to learn? What is all this closure, continuation, currying, lazy evaluation and no side effects business? How can it be used in projects that don't involve a university? Why does it seem to be so different from everything good, and holy, and dear to our imperative hearts? We'll clear this up very soon. Let's start with explaining the reasons for the huge gap between the real world and academic articles.