You've got to remember who Apple are targeting the Pro at though, which is more of the professional market. Designers and the like who use a stylus on a dear daily basis on other devices. Tasks where using your finger is too cumbersome.
Of course you'll get normal users who buy a Pro, and they won't buy a stylus as can get by just as well (better even) with their fingers.
You are right. It's got to be for more advanced users. But why this? It doesn't strike me as this great new product. In the same presentation, they showed the new Apple tv and talked about the tv as the biggest screen. So you take the regular Ipad, Airplay it up to the Apple tv and why the need for the Pro? It's practically a laptop.
The pen, the drawing they showed in the presentation looked great, no doubt. But the Pro, the pen and the new keyboard strike me as uninspired. I used a bluetooth keyboard when the Ipad came out. Same with a pen. And I'd guess my old keyboard is still better than the one they presented.
In comparison, the new tv was at least news. They're on to something there, but I'm not convinced by the Pro (nor the watch). And I say this as a fan of Apple.