the issue is mostly software. not many publishers are open about numbers for games. they give ranges if they give anything. they talk about a few large titles for the year. while npd gave little, it did provide a glimpse of the games launch size.
you also have to wonder how uninformative other companies within the industry may get now. if you dont have a large numbers platform putting your product and its sales out there every month... why should i (or would i) talk about my game being a flop? or being marginally sucessfull.
sales isnt something many american (or euro) video game companies like or will talk about as it is. many of the japanese publishers have been the most open when it comes to disclosing and discussing sales. they have a large platform of companies that collect and make that info public though. american and euro publishers have been increasingly differnt. they dont want a game to be judged by if it sells or not. "if its dead at launch its dead period". it effects the coverage and the way the press talk about the game.
npd still providing a generic no number top 10 speaks to this. it awards big sellers with exposer while not harming anyone.