It's incorrect to look at the concept of ownership from solely legal or solely technical perspectives, because reality is a joint application of both simultaneously.

What point is legal prohibition if technical implementation is trivial?

And what of legal requirements if technical implementation is impossible?

The unwritten assumption girding physical ownership was "... and it's non-trivial and expensive to physically copy a book."

With digital copying, that's no longer the case. Consequently, simply to maintain the same system the law would still need to change.

Unfortunately, in the back and forth between extreme positions, publishers used this difference to argue that ownership was no longer financially possible and usher us into the realm of rent-only.

PS: Valve maintains sufficient control of Steam-distributed apps that's a defensible position. A better case would have been GoG.