Credit card and location data is one thing. If we opened up these devices to the Wild West we’d have spyware that tracks every single thing you do on the phone in real time (and logs all your conversations and everything else). We’d also have malware that gets root access to the phone and breaks into your bank accounts.
It would be a total disaster!
1. The app store is already mostly spyware.
2. Apps are actively encouraged by Apple and Google to be spyware.
3. An app store cannot prevent spyware.
4. Sandboxing is unrelated to an app store.
5. Most source code is not available on the app store, and Apple and Google are actively hostile to open source apps.
6. There is zero source auditing done on the app store.