I’d hate to live in a world without physical books.

The only time I wanted physical books obsolete was in college, because I hated carrying 10lb of textbooks in my bag. I've had a full bookshelf for a decade since then and can't imagine a world where I have thumb through a stupid Kindle menu to see my collection.

I have the reverse. I used to have around 2000 physical books. Every time I moved (and I moved a lot) I'd pack them all up into boxes, move those stupidly heavy boxes, unpack them all. I'd almost never read them. They were just expensive wallpaper. Now I have thousands of ebooks on my hard drive and I carry them all with me when I wander the planet.

That's like saying bicycles are obsolete and we can move on.

Furthermore, it doesn't matter if they're "obsolete." In the case we're replying to, they provide a non-revokable mechanism to reward the author if you decide to "pirate" the E-book. Complaining that it sends a misleading signal that physical books are still in demand is a weak, ridiculous excuse for stealing.