This is a logical fallacy seemingly based on your personal situation. There are a confirmed 12.6 million individual houses which download games illegally, and that was a sample taken over a 3 month span. You assume people who pirate games never buy them, but there is evidence that those who pirate games spend a larger percentage of their income on the gaming market than those who don't. The overlap is high. What we can't know is how many games, if they weren't pirated, would be purchased by the offenders?
Any answer to that question will be conjecture, but it won't be 0. There is substantial evidence that a game which is easily pirated tends to be heavily pirated, while games which are more difficult to pirate less so. There was a game studio who went out of business about 6 years ago, I can't remember the name (Imagination studios? Something like that) which, for every 3 copies of a game they legitimately sold, there were 100 failed attempts to download a pirated version. This has always been a bigger issue for PC gaming as opposed to console gaming because you need to get your physical box modded if you want to play pirated games when it comes to consoles. But if it's easy enough, people are more than willing to do it. I mentioned the original Xbox earlier, and a google search for xbox 360 mod chip makes it clear there's plenty of interest in modding the current system as well.
Steam has found a great, effective way to protect game producers without harming the consumer, and it's been rewarded generously. Those great sales you get? They're available, in part, because the developers aren't losing a ton of profitability from piracy.
And look, I'm not defending the worst of the DRM practices out there. SimCity and Diablo 3 (both of which I've bought) were disasters from a DRM perspective. Always on connectivity, and saving your data on company servers is terrible for the consumer. Short of MMOs which can justify this practice simply because it's a necessary mechanism in game use, it should never be utilized. Of course, the Xbox One's DRM isn't like that. Again, it simply needs a single bit of data sent to a server once every 24 hours. Nothing is being stored on Microsoft's servers, nothing requires a constant internet connection (unless you are playing online) and nothing should damage your ability to play games on your schedule at your convenience. In exchange, developers will be able to make a bit more money per unit shipped, which gives them a slightly longer leash to explore new game mechanics, create original titles or provide game sales, all of which benefits the consumer.