PD is PD until the threat of Copyright Suit
Many of the commenters here have correctly pointed out the fact that without some kind of profit motive, many of these works would never be "published". Look to Dover Publications, a longstanding "publisher" of public domain books. People willingly pay for something free they could not find elsewhere. This is a good thing.
However, if Dover were to run about, sending nasty letter threatening people with copyright lawsuits for "violating their copyrights" -- that they don't really have, except they paid the $20 fee to the copyright office. THAT'S the problem....copyright ABUSE!