I think the practical difference is that the rates that publishers charge libraries for ebooks are significantly higher than what either consumers pay for the ebook or what a physical book costs. See
https://archive.is/Ha3VQ for one example:
> To illustrate the economics of e-book lending, the N.Y.P.L. sent me its January, 2021, figures for “A Promised Land,” the memoir by Barack Obama that had been published a few months earlier by Penguin Random House. At that point, the library system had purchased three hundred and ten perpetual audiobook licenses at ninety-five dollars each, for a total of $29,450, and had bought six hundred and thirty-nine one- and two-year licenses for the e-book, for a total of $22,512. Taken together, these digital rights cost about as much as three thousand copies of the consumer e-book, which sells for about eighteen dollars per copy. As of August, 2021, the library has spent less than ten thousand dollars on two hundred and twenty-six copies of the hardcover edition, which has a list price of forty-five dollars but sells for $23.23 on Amazon. A few thousand people had checked out digital copies in the book’s first three months, and thousands more were on the waiting list. (Several librarians told me that they monitor hold requests, including for books that have not yet been released, to decide how many licenses to acquire.)