the point of functional programming is to not program functionally

closures so you can have state
monads in haskal so you write imperative-like pipelines
progns in lisp so you can evaulate for side effects instead of value

trivial to implement

Indeed, which makes me wonder why don't more people use them.

you can use threading macro

Monads are not just (f . g . h) x

handled in lisp-native ways

Which happen to be extremely shitty ways. There is no reason for the standard to define exception handling if it can be defined by the user in a saner way.