I think there's a few of the biggest problems w/ piracy.
One - Impatience. This is the whole "I can get it online now, download it, and not wait for the game literally to get to retail or for a digital pre-load and unlock" factor. Most games, they seem to be leaked out before the game winds up on the shelves, digitally or at brick & mortar retailers. Often, this leak seems to be around the time reviewers get an early copy or around the time b/t a Game Goes Gold Announcement and Street Date occurs factor. Somehow, it's getting out there.
Two - No DRM around leaked version. You can't beat NO DRM. So, it's either a leaked version that never got any DRM wrapped around it or someone already cracked the DRM. Regardless - less bullshit to deal when NO DRM is involved.
Three - Piracy takes no money out of the pirate's pocket, wallet, or credit card.
Four - No benefits in buying legit version. If the pirated version is the same as the retail or digital versions, what's the point? Programs like Steam and Impulse have their own benefits built right into the client program. Sometimes things like DLC, extra content, and other factors - these can lead to people to buy the legit version.