The whole reason for GOG existing was they strip dead DRM from old games so the work again without "warez scene" cracks; and fix all the OS/driver incompatibilities along the way.

As far as I know all the games you can buy on GOG will be completely DRM free.

Correct, but GOG provides games without _any_ DRM, both in the installer and in the game itself.

> What does the installer matter for DRM-free software?

Requiring a network-connected proprietary client to install the software is itself a form of DRM.

> For software with other forms of DRM built-in anyway, who cares if the installer has it?

Again, GOG does not distribute games that include DRM, whether in the installer or in the game itself.