I'm wondering why Data.Void does not have a Monoid instance, or, what would be the problem if we do "mempty = absurd mempty"?

Long story: I was using a monad with some transformers, then I realize I can collapse State and Reader into RWST with Void being Writer output.

(well, I could have just used Unit but I wanna give Void a try...) I know beforehand that Void is Semigroup but is a bit surprise it doesn't have Monoid instance.