First sale doctrine (in the US) said the buyer owned the physical copy and could resell or do what they wanted with that single copy.^
Obviously, that isn't portable to a zero-copy-cost digital realm.
However, the "buyers never actually own anything digital" modern reality is vastly different than the historical norm, in favor of publishers and platforms.
What was missed was the conversation around what baseline we should establish around digital ownership.
We've nibbled around the edges (you have a right to decrypt something you've purchased, in some cases), but we never clarified it sufficiently.
And without clarity, buyers only get whatever rights publishers/platforms decide to grant them.
IMHO, we'd be better served by establishing a clear floor of digital ownership rights, that no publisher or platform had the legal right to remove or obstruct.
That's how we did it previously, and it worked well...
^ There were some exclusions around mass/public broadcasting, but those were pretty limited.
I'm not sure how you figure that. Its still a sale. You might want to read though how much case law there is all over the world that conflicts with that conclusion. Read that post, it has plenty of examples how it doesn't matter if its digital.
Here is one in particular:
In a 2016 Australian case regarding Valve's refund policy for Steam, Australia's High Court carefully examined whether computer games sold through Steam are goods (and therefore property and consumer rights apply to them) or services (and therefore no property or consumer rights or apply to them), and concluded that they are fully goods, and that Valve doesn't merely sell a license to use the software, but in-fact sells the software itself, and that whoever buys a game from Steam becomes owner of the software that they purchased. Australia's High Court concluded: "Each of Valve’s challenges to the applicability of the Australian Consumer Law fails. The conflict of laws provisions in the Australian Consumer Law did not essentially carve out an exception for conduct by foreign corporations like Valve governed by a different contractual proper law. Valve supplied goods (which are defined as including computer software)."
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.