The 90% mention is an actual figure, IIRC. I forget the game (World of Goo?) but it had 10x as many copies of the game submit to the public scoreboard as actually sold. And submitting scores was an opt-in feature in the game
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Because if the sales numbers were disclosed, they would lose their point. THere's no correlation between piracy and sales. Pirates dont buy games, they never would - so no sale was lost. Those who do buy them are not pirates - they bought a copy and never caused any harm to the company. They understand, and they dont want to admit that since that would mean defeat in the censorship control. Moreover, oh boy, CAPCOM CEO? The same CAPCOM that delivers nothing but shitty half-assed console ports and generic resprited fighters(And then try to sell tons of DLCs on it, because the most powerful chars come in DLC, so anyone playing multi competively will HAVE to buy the DLCs) Oh oh, I wonder why are they losing sales, but it's probably not their shitty business practice of releasing crap.
In truth, I think it's really the middle ground here. Not all pirated copies are lost sales, but some people would buy a game if it weren't pirate-able. A lot of people use DRM free games selling well (IE, Witcher 2) as evidence against this, but the problem is we don't know how well they would have sold without piracy; in most cases where I see this example, the game in question sells well because it's a really good game.
For example, awhile back Sins of a Solar Empire released with no DRM and sold well. It was a fun game, and I bought it (didn't even "demo" it first with a pirated copy); but whenever I played it multiplayer everyone wanted to use hamachi instead of the legit servers (I'm sure you can guess why). The game still did well, but it became obvious to me that a lot more people pirated it than bought it. Combined with my first point, yes, Piracy does hurt sales, possibly significantly, though nowhere near the level of a lost sale for each pirated copy.
However, I'm still not in favor of DRM. This is because current types of DRM simply don't work; they might delay a pirated copy by a week, but even that's optimistic, and the more aggressive ones are a pain for legitimate users. Right now, sadly, the best option for game companies is to go DRM free and write off piracy as a necessary evil. If someone came up with crack-proof DRM that didn't noticeably impact legitimate users, I'd be all for that being on every game ever.