That "selling a copy" did not stop working. Even with piracy, which has been around a lot longer than 10 years, it generates billions in revenue. It's more that it doesn't work for them in terms of the strict control they would like to have over your use of it. But for a sale, protecting a copyright and controlling use may overlap to a certain extent, but are very different things.
Copyright is not impossible to enforce to a reasonable extent. A system where revokable keys to copyrighted content would have to be provided to anyone able to pay some reasonable fee. Their device or application would stand up to a court assessment similar to the betamax and limewire cases (including risk for damages if it doesn't), and revokable keys would make such rulings enforceable enough. That would be enforcing copyright.
Licensing the ability to make devices that can access peoples' purchased content on the conditions that they will only function as content holders see fit is controlling use. That this scheme effectively supersedes any rights that a purchaser might legally have and, more than anything, I think has signified the shift to what could be described as an "Imaginary property" model. Since this model became prevalent with the rise DVD 10 years ago, that would coincide with your estimate.
I don't really see those "free as in beer" people as being all that different from the MPAA/RIAA. They both think they can define what property really means on the basis of the beliefs that suit them, actual laws (hopefully made without corrupting influences) that define such things and related rights be damned. They are just on the other side of the same coin.