de_Monteynard: That is a false argument. If this were true, then GOG would never had gotten off the ground, with either old or modern games. While it does not have the same market share as Steam, is has grown to the point that not releasing here hurts your sales.
However, the main issue we are dealing with here is their very strong pro-DRM stance. It took them a long time to release E1 DRM-free on their website, let alone on GOG. Now that E2&3 are coming out on Steam only, they are trying to whitewash the whole affair by saying that the KS campaign was solely for E1 and that the conditions that applied there are completely separate from future releases.
The problem with this argument is that they never indicated this during the campaign itself and made it appear as if all three episodes of The Banner Sage would be available also in DRM-free form. This led a lot of people, myself included, to increase our pledges in order to receive the whole game, hoping to support a fledgling company with a good game idea.
Consequently, this has become both a fight against DRM in gaming, and against shady practices by companies and unfulfilled promises on Kickstarter.
Unfortunately, from what I gathered, it's true many times for unknown indie games. You need to take into account the costs associated by releasing more than one version (Steam vs GOG vs DRM free on Humble for example).
There are indies that see the light at the end of the tunnel. Defender's Quest, Stardew Valley just to name some games.
But for this Banner Saga title? Even Trine 3? While I personally haven't seen the statistic, I doubt the numbers would be that great.
Maighstir: Yeah, as do Linux users who prefer not to use Steam and bought the game on another distribution platform. Which was my point.
Steam is pushing Linux forward.
If anything, I'd take their stance more seriously than other gaming companies.