Oh boy, I just published a book with photos of all these copyrighted games...

There may be an interesting side note to the comment about the artist who worked hard for the artwork they put on certain games. But in many cases they don't own the rights to that artwork. Some company does and they may just be sitting on it and not care about the relative small demand there is from a few pinball enthusiasts. I'm pretty sure if the artists would have the rights to their own artwork we would see lots of art being available.