Historically, games would refuse to boot unless you had the game disc inserted. Even if the game was fully installed and didn’t need the disc to run, requiring the disc was a primitive form of DRM.

One of the most common forms of cracks was a NoDisc crack, which did exactly what it says on the label; It removed the requirement for you to insert a disc. This was usually just a quick file replacement. So it was easy to take the game disc to your buddy’s house, use it to install the game on their computer, apply the NoDisc crack, and then your buddy could play the game whenever they wanted without using your disc. This was many people’s first intro to piracy. Obviously game publishers hated this, and constantly played whack-a-mole to shut them down.

When transitioning to digital sales, the disc requirement obviously won’t work. You can’t require a disc when the user never actually received a disc. So the game publishers had to remove the disc requirement when they put their game up for sale on Steam. And this is showing that in the official Steam release, a pirate’s signature is found. They simply used a NoDisc crack (from one of the crackers that they had constantly been battling) on their own game, to remove the disc requirement. Instead of finding an “official” way to do it, they just used the most straightforward route.

And yet game publishers still constantly harp about piracy.