1. what about something like a usb flir heat camera? yes i know webusb exists, but having to go to a website to use a peripheral (and give it permissions to that peripheral) is not ideal
2. apps can change on you at any point, potentially maliciously. I'm not naive enough to think the app store will catch this kind of thing every time, but at least you have control over updating apps, and some guarantees that everyone gets the same binary
3. you can kiss any sort of ui-cohesion goodbye