Does anyone know why the game doesn't come with any goodies? I know not every game gets them but given the fact that this is a sprawling CRPG epic, I would have thought Obsidian and GOG would have made sure to give at least some fun goodies (soundtrack, wallpapers, behind-the-scenes documentary, anything).

Agreed. I mean, I like buying games from GOG for the DRM-free nature of them and that's definitely enough to convince me to buy here instead of Steam, but the goodies do help a LOT haha

There was a time when GOG (when it still was Good Old Games) gave goodies with each of their games and that, along with the DRM-free nature of their store, was a great incentive for me to buy my games on GOG first and then maybe look on Steam if there were any sales.

But since a few years they have stopped doing that, games are still DRM-free (luckily) but the goodies are much much rarer. I guess it depends on publisher's choice and there is little GOG can do, but who knows really. Goodies are still given for older games (probably those who also were on the Good Old Games catalogue), but newer games normally don't have them or you have to pay extra for them.