For some reason the US VG market is very secretive about its numbers (i.e. NPD). It is different in Japan, and the movie industry in US is very well reported. Movies have development costs and sales number published without this interfering with the business.

I'm surprised there isn't another

As digital sales become more common the numbers will probably not leave the publishers in the future. Even NPD will have prooblems getting any meaningful sales numbers.
"Collectively, digital game sales accounted for $133 million in revenue according to SuperData. These figures were pulled from from spending data for 37 million customers and include both full game downloads and DLC. Physical retail games according to the NPD generated $235 million."
http://www.gamespot.com/articles/top-digital-playstation-games-generate-twice-the-r/1100-6425560/