This is because monads are terrifically useful for doing a number of things, but each thing is most easily explained in different, seemingly inconsistent mental

This is because monads are terrifically useful for doing a number of things, but each thing is most easily explained in different, seemingly inconsistent mental models. Monads are an abstract, complicated category theory thing (it's a monoid on the category of endofunctors on the category of Haskell types, obviously!) and trying to explain the concept directly is too hard, so people talk about burritos and E-mails and other things that more reflect specific uses of monads than the general thing.