Actually, milkman, as far as I can tell, the ONLY reason that Wal-Mart only carries 'edited'/'clean' versions of CDs is money.
Think about it. The #1 listener of most popular music, especially rock/rap/r&b, is going to be children and teenagers.
An increasing percentage of these releases are ... well, let's just say that in the days before radio edits that they wouldn't have EVER gotten on the radio.
Wal-Mart has a choice: They can either ID people for un-edited music...or force the record labels to make 'clean' versions for sale in their stores, and thus sell a MUCH larger number of albums.
Money is all it comes down to. Games and R-Rated movies aren't purchased quite as often by teenagers, by comparison.