cJether: I don't know if I should say that. I think Gog should allow games with DRM on the shelf, which will attract more games to settle in, so Gog can have more games.
DRM-Free may discourage some devs from bringing their games here, but allowing DRM here and killing off GOG's Unique Selling Point (an immensely bad idea) still doesn't solve the other main issues of:-
1. Laziness, aka,
"Sigh. Do I HAVE to support more than one store, rewrite all those Steam achievements for Galaxy, engage in two lots of support forums instead of one, push two lots of patches instead of one? Why can't people just buy my games on Steam?" attitude by developers / publishers. Many games
on this list, eg, Heretic, Hexen, etc, aren't on GOG despite being able to be run without the Steam client (due to disabling Steam's DRM) and games on that list sold by Humble are missing the DRM-Free builds clearly for reasons other than lacking store-level DRM. And most of the +27,500 out of 30,000 games on Steam that have Steam's DRM aren't sold on other DRM'd stores (uPlay, Origin, etc), so lack of store-level DRM isn't even the main reason why many Steam games aren't on Origin, etc, either.
2. "Exclusive Fiefdoms". There's a reason why you can't buy Mass Effect 3 / Dragon Age Inquisition on Steam or Half Life 2 / Portal on Origin. When the largest game publishers start running their own stores, it just fuels "the exclusive problem" for self-made content. This is likely to get worse with the push for "Games As A Service" and / or wanting 100% of micro-transaction revenue vs only 70% (that for games like Fortnite, etc, is regularly more than what they'd get for selling it at $60 without MT's).
3. The "I want all my games in one place / No-Steam, No-Buy" crowd. GOG could offer the exact same catalogue that Steam does complete with the same level of DRM, but the Steam branding addiction / fanboyism will still run strong. The bottom line is - "The Steam Model" was designed from the start to create a "captive audience". See how angry some are at Epic because some publishers have chosen to not sell their games on
"my store" like some co-dependent relationship.
There are probably other reasons too, but DRM isn't even the main reason why GOG / Epic / uPlay / Origin aren't Steam. It's simply Steam "got there first" and developed a
Monopsony on the back of a "captive audience" by increasingly encouraging locking game features to one specific store by default that then increases future workload on game developers by forcing them to rewrite chunks of their game if they want to support other stores with same feature set, in a way that prior store-neutral physical retail discs (that were identical for everyone) never did. And a lot of people have basically become as addicted to that (and those "social features") as they have Facebook.