They still sell DRM games and steam has been the single most honest store available. If GoG was being honest they would see the steam client as a threat especially when it's the only one actually putting out outside of GoGs loaded key service.
Agreed, and the best possible scenario is that successful Steam competitors are healthy competitors; the kind of companies who you wouldn't mind seeing win the market, or at least shape the market. A lot of Steam's competitors (unlike Gog!) do not fit into that mold.
plus their no-DRM approach is notable.