Businesses really only believe in one thing, profits.
They wouldn't have done the market research because of the ridiculousness of the app. "say, how would you like an app to go on your e reader that replaces all the swear words with nice clean ones that don't offend a handful of people living in the bible belt?"
"Hahahahahahahahaaaaa! That's a good one! Hahahahaaaaa! *slaps thighs then wipes a tear away, walks off still chortling*
"I don't think this is going to take off".
I can see some religious fundamentalist reading some hardcore thriller in bed one night about the criminal underworld, and just after reading yet another brutally violent part where the poor guy who ratted out the head honcho screamed a few choice words as he was getting his fingers sawn off or something, closing their book, sighing, looking off into the distance with a knitted brow, then his wife saying "what's wrong dear?"
"Oh gosh, there is just sooo much swearing in this book!".
I wonder what the late great Frank Zappa would have thought of clean reader, haha.