BadDecissions: Some people like Steam. It is therefore profitable for a company to bring games onto people's favorite gaming platform. "But but we already had that game how can Night Dive to things that aren't specifically targeted to please GOG users?" Because it's not a damn GOG subsidiary.
Some people like GOG, and Night Dive isn't a Steam subsidiary either. They have relations with both, and that only benefits everyone. A lot of the "retroism" games are already on GOG anyway. More will follow eventually. And often GOG has them for months or years before they even grace Steam's shelves.
If people want to remind them that GOG is their preferred platform, then there's nothing wrong with that. If they want to put on the elitist face, it only shows their dedication to DRM-free, you-own-what-you-buy games.