Just because no one cares about you breaking the law, doesn't mean it's OK to do it. Maybe the State would prosecute you for breaking copyright law if the copyright owner is dead, I don't know. I do imagine that legitimate companies, say a book company, would refuse to mass-produce a 50-year-old book from an author who died but whose copyright still exists. I imagine that if Sony wanted to remake Pong in 1024-bit 5-D graphics for the PS3 and knew they'd make a million dollars off of it, they still wouldn't do it, because the copyright is still there, even if the business that created Pong originally no longer existed. If the law was different, then things might be different, and we might be enjoying many more and varied sorts of products.