Check here. Or a repost, if you prefer to read here: As we've previously said, the files are a remnant of old DRM that is no longer active.
They serve no actual purpose, but their removal in a way that would keep all of the game's functionalities intact and stable would be a lot of work. Our tech team is currently swamped with other tasks (i.e. launching a ton of games, the GOG Galaxy project, preparations for the The Witcher 3 release, an much, MUCH more we can't reveal yet).
Since this is *not* DRM (as it does not in any way lock the game), but instead a simple inefficiency in how drive space is used, it's not a top-priority issue at the moment - however, it is one we do plan to fix and there will be updates when we do have updates to share. :)