Read is one of very few classes with stated a deriving technique in the Haskell Report.
Moving it out of the Prelude would break a ridiculous amount of code and involve adding
import Text.Read
as boilerplate to the top of every single module of Haskell source code out there that deigned to include
deriving (Read,....)
among the list of instances derived for their data types.
The cure feels a lot worse than any disease. Heck, read isn't even a member of the class, so this would just spite users and not even address the symptom raised by this thread.
-Edward