If GOG went down tomorrow, those games would be gone just the same as the Steam ones, since I gave up trying to back them up a decade ago.
On top of that, those updates can be kind of useful. None of my GOG games run on Linux, while most of my Steam games run on Linux. Also annoying: None of the GOG games run on a genuine Win9x either, as what you are getting is an updated version for modern Windows, not the original game.
Either way, I just don't think DRM-free is the proper solution for media management today or in the future. The olden days of static media are largely gone and the modern world is just way more fluid. So far none of the proposed solutions are able to capture that properly.