alcaray: Generally developers don't need to be talked into providing updates for their games that people have bought. I don't know if there's some kind of argument between GOG and Beamdog and I don't really care. If they treat like trash the ones who bought their game through GOG, then those consumers should become angry and tell them so. I did so and was ignored (Beamdog is good at that).
I guess we disagree. Be well.
I agree with you: I also bet that Steam didn't need to contact the developers in order to get the latest version of the game.
That said, let me add that your vision of the gaming world is far too ideal to be realistic.
Game stores have both the right and the duty to protect their customers: if a developer doesn't keep their games up to date in a particular store, it damages both the gamer and the store, because it will make the latter lose customers.
That's exactly what is happening lately here on GOG.