Esoteric languages are intriguing and can make you go 'Hmmm...', but what can we really learn from them? Is there a benefit to spending more than 5 minutes trying to write an application in an esoteric language? Have you tried one, and if so, what did you learn?
What can we learn from esoteric languages?
programming languages
Some esoteric languages are important as practical demonstrations of the fundamental concepts. Unlambda allows to play directly with the SKI-calculus, Brainfuck clearly shows the complexity of the Turing machine, Malbolge is interesting in terms of reasoning about the Turing-completeness, etc.