Erm, not to defend warez, but...
If a game is not for sale new, it is abandoned. Those that made it have stopped trying to get paid for their efforts. (Or rather, the big corp rights-holders have decided they don't effen care.) This is a sad thing, but companies continue to do it. Now, it is still illegal to propagate illigitimate copies of said game (despite what some might try to argue), but I'll point to lots of great arguments about how it is certainly not immoral.
Now, in an ideal world, all of these old titles would be continued to be offered for sale. Doesn't happen for DC games or any other games, and it is a shame. A real shame.
However, if the only way I can buy a game is to pay some obscene amount on ebay (try searching for, say, Ultima 1), I'll feel no remorse for downloading said game. (Actually, I got that one as part of the Ultima Collection just before said collection became tought to get -- it is now way too expensive on ebay.) Of course, I'll still look for the original at a reasonable price, if only because I love to have the real thing, the media, the manual, the boxes, etc.