The EU has already done this since the ECJ ruling in 2012, and the US is behind the curve.
That being said, it seems like the ultimate end run around otherwise well established law surrounding books. As you noted essentially all software works in this way. Throwing out all established laws and end user rights "because digital" hardly seems reasonable to me.
How does such a line of argument square with the fact that even making personal use of a digital item inevitably involves multiple copy operations on a local device in the best case? Even moving it between two partitions on the same device involves copying it. (I suppose I should just be grateful that the digital overlords saw fit to grant me permission to move things between logical volumes. /s)
Most digital goods are "sold" as a copyright license.
The argument is simple. Copyright allows the copyright holder to enjoin anyone else from making a copy of a work - including a digital copy. Essentially all software works by making copies of data that is uses.
The first sale doctrine doesn't apply (IMO) because it sets limitations on the rights of a copyright holder to a particular copy of a work after it has been sold. Each "loan" of an ebook is a fresh copy.
If you look at the Controlled Digital Lending website[1], they pin most of the legal legitimacy on fair use, not first sale doctrine, which I think is probably much more solid legal footing.
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1. https://controlleddigitallending.org/