No reasonable being likes DRM, what GOG stands for preciesly fits for the majority of gamers here. However, GOG lacks so many GNU/Linux ports which are already on Steam. More to the fact, if you are aiming to run a Windows game via an unofficial source port, you will need to run GOG's Windows installer via WINE in order to extract game data. In the case of Steam, we can simply use SteamCMD to get uncompressed game directory. That is my sole reason of prefering Steam over GOG.