The entire selling point for this site is that they sell DRM free games.

Since the games are DRM free, you never have to worry about the publisher, or anyone else, pulling servers offline and making the games unplayable.

GOG can go out of business the day after you purchase and you still have the games you already bought and downloaded.

They're not a game backup service. They're a game store. Once you've bought and downloaded your games, you can make your own backups; you don't rely on them to keep anything available forever.