Don't fall for self-insignificance syndrome. ;)
Lots of devs do care about selling their game on GOG. Devs usually know that DRM is stupid. It's publishers being negative about DRM-Free, because they often have bad knowledge of real world, living in ivory towers, and they like oppression.
GOG sell a lot of game copies, and it's an effective mechanism of motivation to remove DRM from games. You can look how Sony cared enough to publish Horizon Zero Dawn on GOG on launch. It's not a shabby thing to happen. And in case with Denuvo removal. Many games that gets Denuvo removal being published on GOG first, with Denuvo being removed from Steam version happens later. It's a hard evidence of industry's recognition of GOG.
We have devs that prefer to totally remove their games from Gog rather that providing here a patch that they already provided on Steam. Also HZD was released here months after the original PC release, same thing for Days Gone which we are still waiting to be release here, and no news about Death Stranding despite Denuvo being removed months ago.
Some devs like Gog and like to release on Gog, but I don't really think many "needs" to release one Gog, If they are on Epic and Steam they already cover 90+% of the PC market.
There is also a difference between removing Denuvo, which is something that don't really require any works as the Denuvo-less version is the one used during development and actually implementing an offline mode for a game that didn't had one.
Dev's probably do not want to re-work their game to work from a huge market (Steam and/or Epic) to an unfortunately much smaller market (GOG). And this is going to be a continuous problem, as proprietary stuff exists for each platform - and especially if games get released first on say bigger platforms like say Epic or Steam...and then get ported over to GOG.
They can't just copy & paste say games from Steam to GOG w/out much muss or fuss, if say they decide to lean into Steamworks for stuff (Cloud Save, Achievements, Multiplayer, etc) in that version...and then bring the game to GOG.
GOG has Galaxy, which has also their own set of this stuff - which I'm sure they'll have to re-code and re-work, to support a GOG version properly.
I'd also bet the vice versa is true, if a game starts say on GOG Galaxy with those features for Galaxy (Cloud Saves, GOG Galaxy Achievements, Galaxy Multiplayer, etc etc)...and then they bring the game over to Steam. Then, they have to re-work the game to bring it onto Steam, to utilize Steamworks & all of those features.
We need middle-ware again, like GameSpy - but something that'll actually stick around....so that dev's can have a game on both GOG and Steam - and eh, they don't have to re-work code to support prepriatary systems like Steamworks and/or Galaxy. This way, they ain't wasting time on having to do a version for every store, every time the games gets updates on one store, but then needs to get an update on another/
And honestly, games should have built from the ground-up into their engine profile support to save games locally on the PC - multiple player profiles offline; Achievement support in-engine OFFLINE; save games while offline; and stuff like that.
But, let's be real here - as games get more DRM'd, it's likely in a few years, when support is cut...they'll just re-release and remaster the game again so they can try to get us to buy it again. I mean, c'mon - when's Skyrim and GTA5 getting another re-release, right? ;)
I bet it's real easy for old games like say Quake 1, 2, 3, and 4 and any of their expansions (if they have any) to bring from say retail to GOG to Steam to Bethesda Store to Xbox for PC Store say whatever w/out much porting - as none of this in the old days had say Achievement stuff; online-only stuff; and whatnot; that stuff wasn't really even a thing. They could just bring it over to each platform, bare-bones style - without any of the non-sense.