Because sandboxing on iOS is terrible. Not that any of the other commercial vendors are any better.

If they could provide good sandboxes do you think the highest security certifications advertised on their website [1][2] would only certify protection against attackers with “basic attack potential”, the lowest possible level. Three whole levels below “moderate attack potential”. I mean, seriously, they certify their security sucks on their website, is it any wonder their security sucks.

[1] https://support.apple.com/guide/certifications/ios-security-...

[2] https://support.apple.com/library/APPLE/APPLECARE_ALLGEOS/CE...