The funny thing is that Steve Jobs vision was that all apps would be web apps. Apple don't want to sell apps, they want to sell devices. And for people to buy devices there need to be great app's. The reason why they didn't go with web apps is that you wouldn't be able to utilize 100% of the hardware capabilities. But it seems to get harder and harder to do low level stuff on Apple devices, so maybe they will eventually get to something that is close to web apps... But if PWA's works on other devices too, I don't think Apple would want that.