amok: I know you are joking, but Tyranny is a day one release as well as Pillars of eternity. There are also classics like sword of the stars, Europa universalis and Hearts of iron. I think they have quite a few data points to compare.
Not to mention that they are also bringing the new Battletech game to gOg, it does not seem that they are ignoring this outlet. Other reason s are Mayne more to do with technical issues, such as MP tied to Steamworks or simillar, and it is not cost efficient to redo them.
The difference is that Tyranny or Pillars of Eternity are games they only published. They may well simply have agreed to let Obsidian release the game on GOG, but they obviously aren't ready to do the same for their own strategy games.
Another issue is that in the case of games like CK 2 or EU 4, the whole multiplayer is tied to Steam and they're using Steam Workshop for modding access. It would probably cost too much to redo the whole thing to port those games to GOG.
Especially since when CK 2 first came out, Paradox also released a DRM-free version on Gamersgate, but they said the sales weren't large enough to warrant supporting that version, so it hasn't been patched in years and none of the DLC or mods work for it.
At this point, I think it's obvious they've pretty much given up on having non-Steam versions of their newer games.