But your timeline is wrong there. DRM already existed, it was all over the place on PC games. Digital distribution was barely there.
Steam's innovation was to wrap the DRM into a full-on digital distribution platform. This is a good couple of years before Microsoft put one of those on the Xbox 360, and many years before they made full price games available on it. It's before the Apple App Store. Before World of Warcraft (although in fairness after EverQuest). Before Netflix. Before Spotify. It's before anybody was tying your digital "purchases" to a persistent account.
There's no reflection of PC value on other publishers not having their own take on Steam, Valve simply came first, before anybody else on any market or any platform. They were not the first to point out that curbing rampant piracy was as much about making the commercial alternative more convenient as well as more secure, but they were the first ones to implement it (poorly) and to improve fast enough to actually realize that idea.
They invented games as a service. Ground up. Day one. They are the prototype for digital distribution worldwide.