Comment by kadoban

The practical example is being able to use the same names and utility functions and such on all of the different monads. That's kind of it.

Other than that it's just nice for communication in the right groups, it's shorthand for a whole bunch of properties that you then don't have to explain.

It also only really works super well in languages where the type system is expressive enough to allow that (or just permissive enough not to stop you I guess), so that mostly comes up in fun "functional" languages where they spent a bunch of time on the type system.

You'll probably understand a bit better if you take some time and learn/use Haskell a bit (if you don't already understand, it kind of sounds like you do tbh). It's a fun and educational language in a bunch of ways IMO. It depends on the kind of person/programmer you are if you'll really care though.