You have to remember, the STH backmasking was a ploy to sell more records, most likely. You put that in there, tell people it's there, and they ruin their records playing them backwards. Now, they need to shell out another $7.99 for a new one!
The Pink Floyd was on obvious attempt at poking fun of this whole ordeal.
Has anyone ever tried the "Dark Side Of The Moon/Wizard Of Oz" conspiracy? Or the "Willy Wonka/2112"???