Setting aside the ideological arguments, the primary reason you should not be installing video drivers, or any other device drivers, outside of what your distro

Setting aside the ideological arguments, the primary reason you should not be installing video drivers, or any other device drivers, outside of what your distro has packaged (if you can help it) is that they have an annoying tendency to break when you do a version upgrade leaving you with, if you're lucky, only the ability to log in via the command line or ssh. Worst case, you can end up with an entirely hosed install. Even if they work (for now), keeping them in sync with the rest of your system can be an exercise in frustration. As someone who is currently dealing with proprietary AMD drivers (and previously proprietary nVidia drivers) on Debian testing, it's pretty much only a matter of time before things will break... you've been warned but I understand if you need to do it anyways (as I do for compute support with AMD currently.) I'm very much looking forward to the day when we have Debian packages (at least in the non-free repo) for current AMD GPU compute stuff.