Many years ago, I briefly worked at NVIDIA on the DirectX driver team (internship). This is Vista era, when a lot of people were busy with the DX10 transition, the hardware transition, and the OS/driver model transition. My job was to get games that were broken on Vista, dismantle them from the driver level, and figure out why they were broken. While I am not at all an expert on driver matters (and actually sucked at my job, to be honest), I did learn a lot about what games look like from the perspective of a driver and kernel.
The first lesson is: Nearly every game ships broken. We're talking major AAA titles from vendors who are everyday names in the industry. In some cases, we're talking about blatant violations of API rules - one D3D9 game never even called BeginFrame/EndFrame. Some are mistakes or oversights - one shipped bad shaders that heavily impacted performance on NV drivers. These things were day to day occurrences that went into a bug tracker. Then somebody would go in, find out what the game screwed up, and patch the driver to deal with it. There are lots of optional patches already in the driver that are simply toggled on or off as per-game settings, and then hacks that are more specific to games - up to and including total replacement of the shipping shaders with custom versions by the driver team. Ever wondered why nearly every major game release is accompanied by a matching driver release from AMD and/or NVIDIA? There you go.