GOG commits its own resources to maintain classic titles playable, now and in the future. We are launching the program with 100 games and will add more in the next few months.
Yes, they're looking to continue selling older titles and your point is that pirating / torrenting is free, but GoG are ensuring the game will actually run on a modern machine - the pirated ones will have problems (not even covering the potential malware ridden ones)
I've been there, done it, got the t-shirt, the t-shirt faded, got ripped and is now a rag somewhere... this is a good move by GoG.