Yes, that's right - Epic Games. Phoenix Point is an exclusive to Epic Games for about one year. I wanted to buy it, but don't want to sign up to that company.
Likewise, I'd prefer to use GOG for certain other games, but the time it takes for games to come onto the platform has sometimes meant I've opted for Steam. Being DRM free is a good thing with GOG, but I've no doubt that one factor isn't enough to stop gamers from choosing a game on steam over GOG, especially when the price is lower or the release on GOG isn't even confirmed never mind delayed for months. And it's likely many gaming companies avoid GOG for the lack of DRM.
Let's face it, Steam is usually cheaper, too, particularly when using a site like G2A to obtain Steam Keys on the cheap. GOG keys are usually a lot more expensive.