They are important in Haskell because they allow "real world" tasks to performed and give the ability to reason about functions. They are _useful_ for non-pure

They are important in Haskell because they allow "real world" tasks to performed and give the ability to reason about functions. They are _useful_ for non-pure function programmers because it's a tool in the tool box which can allow them to write composable code that can be reasoned about. Java's & C++'s Optionals are monads, Rust's Result<T, E> is a monad, etc.