Why are there no big applications written using functional languages?

Because there is no such thing as a big application. There is only bigger or smaller. This is a central tenet of functional programming. “Big application” is a euphemism for “My idea of programming does not scale beyond this point.” You don’t realise how much information you give away when you ask this question.

So can we can stop with the piffle and get on with the interesting and important stuff? Ta.