Ok, there's more to it than that. More knowledgeable people than myself have written articles and blogs on the subject, but I'd just like to add my voice to the crowd.
I'll start off by saying I think there are some reasons to pirate, though they are more than anything mere excuses. First off, pirating to use as a demo. It's an unfortunate state of affairs that video games rarely come with demos. At one time, you had a demo for almost every game and usually it was basically the first level straight out of the game. The benefit of a demo can be significant - for one, you can not really trust reviews. Mass Effect is a game praised up and down all sides of the internet, the reviews picture it as a gleaming beacon of hope in the RPG realm, and reading those
10 hours later, I removed it from my PC. I found it to be boring, ugly, and the combat sucked. Then again, I don't have a lot of good things to say about BioWare games since Dragon Age: Origins... but that is another matter.
The point is, I wish I didn't buy it. To really know if a game is any good, you have to experience it for yourself. Without a demo, there's only 1 way of doing that, but it is illegal (and rightly so). I'm extremely glad KoA: Reckoning had a demo because for me, it let me realize that I am not going to really enjoy that game. I know a lot of people love it - it is rated 80, 81, and 85 on the 3 platforms it was released for (Metacritic scores). Yet for me, I'd give it about a 6/10. If there wasn't a demo, I'd have been rather upset at wasting $60 on the game. Not to mention there's no returns on PC games, nor reselling. You bought it, you keep it and it's just too darn bad if you don't like it.
Secondly, demos will highlight for you whether you are even able to run the game. Some games just don't like certain hardware, or maybe it's just too demanding for your setup. Imagine finding that out the hard way (I think we've all done it before). The problem here is quite often that the listed minimum and recommended specs are barely reasonable and often vague. There's a massive difference between "minimum" driving the game at low settings and 60 fps at 720p vs the game chugging along at 20fps at 640x480... yet who knows if that's what they mean by "playable". And recommended? Please. Not once has recommended been enough for Ultra settings, maybe not even for medium at 1080p.
If you choose to partake in this practice and you find out you really do like the game and want to finish it, then go purchase it legally! I realize this can take a lot of willpower since you already got your hands on it for free, but you know it's the right thing to do.
The second reason I can see piracy as being reasonable is if it is otherwise impossible to get a hold of the game. I mean literally, it is just not sold locally nor will anyone ship it to you. Or it's simply non existant anymore, like maybe an old SNES game. (Check out http://gog.com for a huge amount of classic PC games at cheap prices!)
Some people like to claim that they are protesting against a company, whether it's because of changes to the game that you don't like, or the inclusing of some arbitrarily "evil" Digital Rights Management scheme. I'm sorry to tell you this, but that doesn't cut the mustard. Simply by downloading the game you are clearly showing you are interested in the product. If you weren't, you would ignore it like all the Wii shovelware collecting dust. Protesting a game can only be done, really, with a boycott. Nobody playing the game means nobody is interested in it - playing the game even without paying means it has value and they should keep going, just with stricter DRM.
That's the problem. You pirate to "protest" something like DRM, and they ramp up the DRM. To put it in a strawman argument, it's like shooting cops to protest that there are some asshole cops. Guess what, that is not going to work, all it will do is bring in more authority. If you don't like DRM, then do not consume the product. Otherwise, deal with it. (See article linked below for more on why DRM is nearly a non-issue blown way out of proportion)
If a game is engaging in practices you find intolerable - like day 1 DLC (See Mass Effect 3 and Sim City 5), pirating it will not send the message that you want. What you want is to say "I disagree with what you're doing so there! Give me everything I want!" like you think it's a hostage situation. The company does not see it that way. They see people stealing their product. They have every right to sell a game how they see fit with whatever features they see fit for whatever price they see fit. If nobody bothers playing their game, then they know they need to change. If millions of people play it without paying... they'll just go to somewhere they can get paid from those playing it (read: consoles).
In the end, the only thing piracy hurts is us gamers. The days of PC dominance are fading into distant memory; PC gaming is now an after thought. If we're lucky we get a game ported, at release, with some customization options for graphics and controls. Often, though, we have to wait for our version and aren't even able to set a custom control scheme.
I've heard arguments about how it's because developing for PC is hard, there's so many variables in hardware, PC gamers are more picky, etc. No, the reason PC games aren't very popular with developers is because PC gamers pirate everything that isn't "nailed to the floor".
As a collective, PC gamers need to really step up to the plate. We have systems vastly superior to consoles, and often a fair bit more expensive too. On top of that we can purchase and install games without leaving our chairs, and usually at around $10 less than console games. And while we wait, we can browse sites like Reddit and YouTube to keep ourselves entertained... yet, apparently, we can't be arsed to lay down some money on a quality product. We get the best deal out there, and we throw it in their (the developers/publishers) faces!
I realize that a lot of this sounds like conjecture and opinion. Well, it is... however, I also felt the need to write this after reading this extremely awesome article on the subject matter:
(Bear in mind it is now a little over a year old data, but it's good nonetheless)
I think the article pretty accurately describes my stance with the following quote. This, my PC gamer friends, is why we must pay for our games. This is why developers don't care about us. This is our own doing.
In summary, looking at the data we wind up with what appear to be roughly equal proportions of machines capable of gaming in the console market vs. the PC gaming market: there are approximately 76 million or more 'next-gen' consoles currently in use around the world; and of the 1 billion PCs globally, we can state with a reasonable degree of confidence that at least 80 million, possibly as many as almost 200 million of them are capable of gaming with the latest titles. If we want to refine the figures down to which machines are capable of 'hardcore' gaming, then we can exclude the Wii from the console stats, bringing us down to 40 million consoles (XBox 360 and PS3); and even if we halve the number of PCs with add-in graphics cards to 40-100 million to account only for medium and high-end graphics cards, we still wind up with at least a 1:1 ratio in terms of the number of gaming consoles vs. the number of gaming PCs. What we can say with a high degree of certainty is that at no point does it look like gaming PCs are being outgunned in terms of sheer volume of console hardware by a 4:1, 5:1 or higher ratio as game sales ratios would suggest.
As in, consoles have at best the same install base as game-worthy PCs, but they outsell more than 5x the amount of games. Talk about shooting ourselves in the foot.