blind3rdeye: I'm also keen to get Hades on GOG. I've been holding off on getting it on Steam. I'm not a fan of Steam; and I haven't bought a game on Steam (or Epic) for more than 10 years. I don't want to break that streak!
But yeah... I do want Hades. I still think there's a decent chance it will appear on GOG one day. All the other Supergiant games are here, and I'm under the impression that a couple of them took a long time after release before coming to GOG. So that pattern may continue.
But as others have said, the only official response from the developers has been something along the lines of "we have no current plans to release on other platforms, but that may change". (I read a response like that on their discord channel about 6 months ago.)
I'm not really sure what makes developers choose to bring games to GOG. But since GOG has a games wishlist, I assume that sometimes GOG approaches developers to try to encourage them to bring their games to GOG. I wonder whether that has happened with Hades yet.

Orkhepaj: why not? those are just stores like gog and i think hades has no drm in it
* I'd prefer to support a DRM free store, even if the particular game I'm buying happens to be DRM free elsewhere.
* I'd like an offline installer.
* I'd like the game to be part of my GOG collection, because my other games of that type are also on GOG. It helps me remember which platform things are on.
* I dislike the direction Steam has gone in recent years - in particular, I dislike that I can't prevent games from updating; and I can't remove their 'what's new' advertisements from the main page of my Steam library. So I'd prefer to not use Steam.
* I'd also prefer to not use Epic simply because I don't want to install a store-front for a single game. With GOG, I don't have to install anything other junk to get the game. I can just install the game directly with the offline installer.
...
I think those are the main things. But also, I don't particularly want to get into an argument about this. It's really just my personal preference and my reasons are my own. So please don't try to argue about it.