It's not. They want you to pay them for the book instead of just getting it for free.
Luckily, for now, piracy doesn't seem to be making that huge a dent in author income as far as I know. Many people find it easier to buy their book with one click on Amazon or one of the other storefronts, or read through a bunch of books with a single Kindle Unlimited subscription.
I'm not sure how long that will last. Some authors are updating their business model to include subscription services like Patreon, where they sell more direct interaction, character naming rights, early access, and additionally gated materials to dedicated readers. This is probably good to secure their income stream in the long term.
One copy in memory can serve millions on your website.
But they have to download it, and you might not have the bandwidth to service millions of downloads in less than a few hours ….
Yes, just so. The parent seemed to be arguing that it was too much to claim that it would take a few hours. I'd definitely call 22 hours at least a few!
My mind was dead-set on the printing press analogy for some reason.
I think there's a somewhat irrational fear from publishers that anyone with a personal computer can create 1 million copies of a book almost instantly (ok, maybe a few hours, depending on disk speed), and distribute them almost as quickly.
I imagine there were similar fears of the printing press from book scribes back in the 16th century.
The reason why the fear is irrational is that the digital mode of distribution is actually constrained by the inherent ability of people to consume new information. You can read only so fast, so it makes no difference if you have 1 million different books "stolen" on your computer. Most of them would have never been read or even opened.