It would just be limited to 3 apps per device that require to be refreshed every 7 days to continue to be able to open them.
Web apps are a non starter for iOS since the only allowed browser on iOS happens to not support crucial standards and may drop your app's persistent data.
Yeah...
> then why not use a Raspberry Pi or something?
Because a Raspberry Pi would be very inconvenient to use as a smartphone, obviously. Doesn't explain why it makes sense to treat one ARM computer as a mildly locked jail (Macs) and another as a hard locked jail (iPhones and other handhelds); I feel like the only explanation here is that the smartphone duopoly has worked hard to condition customers into accepting this.
This is older than the current smartphone duopoly; IIRC, with a few exceptions like the N900 and the Palm Treo, cell phones were always very locked down. It probably came initially from the phone companies being control freaks, and wanting to restrict which devices (even mechanical ones with no electrical or radio interface) could be attached to their phone system.
> N900 and the Palm Treo
Performance-wise, a modern iPhone is more closely comparable to room-sized (building-sized?) supercomputer of that era.