Yes they are cheap, but is a 17-18 dvd / 3 bluray game acceptable? Manufacturing costs would be high, and the user experience would make you want to shoot yourself, 17dvds? fuck meee.
As for a download. I don't know if that is economically viable at the moment. The bandwidth of sending that out to hundreds of thousands (to millions) of people would be quite expensive. It would take days to download. Our buddies in the EU would be totally fucked (some here as well). And it takes up 150gs which some people would refuse to install in the first place.
Ya not everybody has 100Megabit unlimited cap broadband.