Cheating is the only word used to describe this kind of scenario, because it paints such a colorful picture. It promotes the idea that Capcom somehow has something it could be giving to fans, but is holding back a product in order to push more sales on another platform. But why do this?
Why not make money where you can and call it even? What advantage is there to gain from punishing those few pirates out there? Everyone knows that if a game can be stolen, there's really nothing to stop that from happening. So why is Capcom backing out of delivering a product that's pretty much complete? Simple answer: they're just plain lazy.
There's no other clear explanation for it really, because every other answer to the question is far worse. Just picking apart Yoshinori Ono's response to 4gamer provides everything we need to determine Capcom's motivation for this. Street Fighter IV held some extremely strong sales worldwide, as fans who were perhaps split over the whole Playstation 3 versus Xbox 360 debate could come together on a single platform to play against one another. Very little fighting game competition on the PC probably made sales even easier for Capcom, but naturally anything that winds up on the computer is rapidly pirated.
Most would imagine that the goal of not releasing SSFIV on PC is to teach the pirates a lesson. After all, there's no better way to punish someone for illegally downloading a product than just not offering the product to copy in the first place? But anyone playing games online in the past five years knows that things have changed, and while some companies will boast their games un-crackable, more realistic developers know that piracy is something that cannot be stopped. But it can be discouraged, and to an extent controlled. That's why more and more dev's (independent and otherwise) are using platforms like Steam to launch games. The point isn't to punish players, but rather to guarantee the game's release in a fashion that everyone benefits from. Developers still make money for creating a fine product, and players can still play their favorite games (though with a few extra stipulations tossed in).
The fact that Capcom refuses to partake in this process completely just makes me think they're lazy. What do they have to lose from participating in Steam? Not much, considering how well the last version of their popular fighting franchise sold. There is still little competition on the PC for such a game, and many Xbox or PlayStation owners would be more than happy to purchase another copy just to open up a new world of opponents. Their claim of it not being 'fair' to non-Steam owners is also probably one of the weakest excuses I've ever heard. Steam is not only a free service which gives safe access to games, but it also runs on every kind of computer on the market.
All signs really point to Capcom just not wanting to make the effort, satisfied with their console sales regardless of having a 99% complete PC version. It's certainly disappointing to consider, particularly when there are so many reasonable alternatives to prevent PC piracy. If they were truly attempting to fight piracy, they would work hard to release the game with the use of a safe-service, or announce that they were working quite hard on a copy protection program.
Unfortunately, it doesn't appear as though that's the case for SSFIV, and Capcom seems more than willing to just let fans sit and hope that something is done. It's a shame really, since Capcom only really has profit to make from the PC community, and keeping a game away from them is only going to make everyone involved feel alienated and (in a sense) disrespected. After all, why punish the noble majority for the actions of a few selfish individuals? In the end, the only real answer is that it's because Capcom is lazy and just doesn't want to deal with the problem.
Sure they could develop a copy protection program, or team up with an online game provider. But they could just as easily not, and tell their customers to just buy a hard copy. Call it what you will, but it's very clear that Capcom isn't really doing anyone a favor by not releasing the PC version. Just punishing everyone, indiscriminately, because they just don't care one way or the other.