Steam is very much one of the few reasons why PC gaming is still alive and well today. It is a closed and proprietary platform for sure, makes Valve a lot of cash. So much in fact that they have no need to keep developing games. We live in capitalistic world, but if you can get past that you have a central platform from which you can manage your games, their addons, DLC's and even mods. Steam keeps your games up-to-date and provides many services to help you connect with people, like multiplayer games or sharing stuff. It syncs saves to cloud, keeping them safe in case your HDD crashes or something.
Without Steam developers and publishers would need to design, develop and maintain their own solutions to provide these same services. With multitude of different solutions, your computer would be cluttered with them and their quality would be nowhere near Steam. Just look at UPlay, all of those solutions would be even worse than UPlay is. Origin is actually pretty decent and it even has money-back guarantee, something that Steam doesn't have (yet at least).
Basically PC gaming would still be in the ages where managing your games, their addons, DLC's, mods and even updates would still require a lot of manual labor, like FSO does (or used to depending on how you view the situation today). Compared to the consoles, the situation would be so bad PC gaming would have probably died off. So you can thank Valve and Steam for being one of the few reasons why PC gaming is still kicking today. Heck, Steam might even be the most important reason.
And last but not least, as far as I know Steam has been very friendly to indie developers. Steam provides the necessary support and publicity to indie developers to get noticed. PC indie game scene has definitely improved the same rate as Steam's indie support has.
I don't know about you, but I love how easy Steam makes managing my games. Sure Steam itself is DRM, but as far as DRM goes its really good at staying out of user's way. At least if your games are legit and you have solid internet connection.
As far as GOG goes, most of their games are old (well duh?) and thus have no need to stay up-to-date, support multiplayer services, manage addons, DLC's and mods. But assuming they did, then GOG would be out of luck without something like Steam. It would be unreasonable to expect people to visit their website, download game installer, install the game and then left to their own devices as to how to keep their games up-to-date, set up multiplayer games and manage all other relevant ****.
Comparing Steam to GOG is like comparing apples to oranges. It really is.
is FreeSpace on Steam confirmed officially or is it just speculation?