It's an opportunity to make a lot of money, that's exactly the reason why Blizzard is doing this, it's good business and there's nothing bad about it. There has been huge demand for it, and Blizzard decided to provide after they realized that it's worth. Also, since there (most likely I hope) won't be WoW tokens, players playing exclusively Classic will have to pay subscription, so on this end it's safe to say that subscription wise it will make more money than retail in first few months and then it will become steady stream of money for a game which won't need further development after they release all Classic content. It is a money maker, let's not pretend it's not, Activision Blizzard is still a business and it's essential for them to make profit (again, there's nothing wrong about that).