Academics vs The Real World

An ``academic'' programmer takes the most constrained programming language imaginable and uses it to do mundane things.

A ``real world'' programmer takes the most mundane programming language and uses it to constrain the imagination.

Monad is just one of typeclasses. And a typeclass is some abstract entity, that allows concrete types to use some functions. And the nature of these functions depends on a typeclass of a concrete type, and how these functions implemented for a concrete type depends on the embodiment of the typeclass of that type. For example, monad Maybe is a type, computations, embedded into a monad of which, return either result, embedded into one of its data constructors, or a second data constructor - Nothing. Naturally, abstract types are often implemented in terms of type-class constrained polytypes and extraction functions from/to the abstract type families of polymorphic functions to/from some concrete type. However, the definitional structure of an abstract type uses interface operators and, therefore, is not affected by changes of representation. which may be logically hidden and, sometimes, even physically unavailable.