Why not track Digital Sales when the Companys do give out that data? Star Craft 2:LOTV has sold over 1 million.

[Trunkin]

Chazore said:
Would be nice if they did but I can't see it ever happening unless it's going to be used in a way to debase the platform.

Also Steam spy isn't consistent nor concrete accurate either.

Neither is VGChartz, but as least it's better than nothing.