But then why do people want the iPad Pro? That's a LOT of extra money to pay just for a bigger screen.
iPad Pro is the cheapest current-generation iPad in terms of both $/pixel and $/inch. I disagree that it is a lot more JUST for a bigger screen. If you happen to need a bigger screen, it's a fair price, even without the pencil. Of course, the pencil greatly increases the desirability of a bigger screen, which is why they were introduced together. But Apple could easily introduce next iterations of the other size iPads that are pencil-compatible.