Steam DRM is trivial to circumvent, it’s basically cheap locks screwed onto the game with security torx, not even riveted: If you have a toolbelt you’re already in and every skiddie with half a brain cell can do it as Valve doesn’t bother defeating the scripts that are floating around.
What it does prevent is random tech-illiterate people copying game files to their friend’s box.
If Steam dies one day then my library would be largely lost, yes, but not due to DRM but because most of my library isn’t actually on my disk.