You'd lose a fair bit of the verbose and helpful error messages for one thing. I think elm seeks to always have the error messages tell you what to do next, and

You'd lose a fair bit of the verbose and helpful error messages for one thing. I think elm seeks to always have the error messages tell you what to do next, and that might be too tough with type classes. Also typeclasses make me act a little too clever. I have a better time when I'm a little more verbose.