What could possibly happen to PC to make it as closed as consoles? The closest thing might be what Microsoft tried with the Windows Store with Windows 8. And our benevolent PC store monopoly has since then invested heavily into ensuring that PCs remain open.
And they did it in such a way that it cannot be taken away. Even if Valve went away tomorrow Epic and GOG are poised to take their place. And every single PC sold by Valve will keep on working.
PCs aren't even restricted to the x86 platform anymore. Thanks to FEX even your smartphone has become a PC.
And as to why I still keep my physical drives? I still have physical games. I can still get old ones used. And even new ones are released every now and then. On top of music and videos also frequently being released on optical discs.
The solution is exactly what Valve and GOG are doing.