Nice idea, except when new drivers are worse than their older versions. Nvidia has done this a few times by releasing new drivers with support and optimizations for newest model cards that fucks something up on older model cards. A recent example would be the 190.xx series and Fallout3. My GTX 280 runs the game great on 186.xx series and back, but toss on those 190.xx series and it's lagging and freezing at random.
This also is why i'm careful about what games I purchase on Steam. Again, Fallout3 as an example... Steam forces the game to it's latest revision, and on PC that means the VATS bug Bethesda has chosen to ignore. With the retail version, I can leave it at it's release state and it's fine; no update, no problems.
Anyway, I don't think "average Joe/Jane PC gamer" would use a digital service for gaming if he/she had an "average joe/jane" understanding of PC's in the first place. Odds are, if they know how to utilize the service, they probably already know how to update their drivers and do so accordingly...if they don't. well, they need to get educated. (I don't mean any disrespect though)
Readme's and everything else under the sun have been harping on it for a decade now.. "Update your drivers!!!!" While in some cases it helps in others it's just a scapegoat for support helpdesks that don't want to be bothered when a game requires a patch mommy and daddy publisher doesn't want to pay to have issued.