The Functor, Applicative, Monad talk

Functors, applicatives, and monads are fundamental tools for some programmers, yet for many others they are considered immaterial. Indeed there are extremely few languages which offer support for even talking about these concepts. Why then are these programmers so fixated on them? What about them makes them so desirable and necessary? In this talk we will explore the what and why of these concepts and hopefully leave you understanding, if not convinced of, their utility.