Steamworks is a toolbox that is designed to help developers and give them access to new features and is one of the big feature sets that many people don't really understand or talk about - same like Vulcan, Proton or SteamPIPE.Whether Valve planned Steam to become what it is at the start means nothing when they started to capitalize on it. It didnt take long for Steamworks to come along and offer a drm replacement.
SteamDRM is one feature within the Steamworks toolbox and is optional. You can publish your game without SteamDRM but then you shouldn't expect to access all Steamwork features (like dedicated servers, marketplace, free matchmaking) that are run by Steam or people could sell / gift cracked games on Steam or play any multiplayer game with a pirated version. Getting access to A LOT of free multiplayer features with the only downside of having a free DRM in place - sounds like a good deal for most multiplayer games.
You can even release a multiplayer game on Steam without SteamDRM but then you can't access all of the other (multiplayer focused) Steamwork features but still some. Or you release it witout SteamDRM and create your own full automated backend service.
Complaining that Valve introduced SteamDRM with Steamworks is like complaining that your operating system got a security patch.