it hurts developers/publishers because old habits die hard. If you pirate because you genuinely can't afford the game, why would you suddenly stop pirating when you're just barely squeaking by? For everything that you might want, including saving more than 10% of your annual salary, there's always something that has to be cut, and choosing to cut something you can't pirate isn't going to be at the top of your list if you've already gotten into the habit of pirating.
I get that there are students working their way through college that have student loans and credit card debt that get a console from Mom and Dad, and that they genuinely can't afford games for it. That doesn't make pirating morally or legally OK.
That harm is speculative an indirect. If I were to pirate Big Game because I can't afford it, that doesn't hurt developer of Big Game, regardless of whether at some point in the future I might be able to afford other, different games. If however, in the future, I pirate those games I could afford rather than buying them, I have hurt those developers, and thus have committed a morally wrong act. The initial piracy, however, of Big Game was not morally wrong because no harm came of it, or at the very least only becomes wrong at the point where the habit I developed causes me to not buy a game I might otherwise have bought.
I'm going to take an even stronger stance than that, however: there is nothing morally wrong with pirating any media that the pirate would not have bought anyway. There's also nothing morally wrong with someone pirating a game when its price is at an unacceptable (to them) level, and then buying the game when it reaches a level they are willing to pay. I'm not making any claims as to how many people actually behave this way, but as a theoretically matter I would say those actions are perfectly morally acceptable.
Legality is an entirely different issue, of course.