[tempay]

There is a perk to this method. If the user has a (encrypted) backup of their phone then the backup can be restored to a new phone and keys can be generated. If not replacing a smashed screen would result in the keys being lost, with very little gained in terms of security. I think this is one of the places where added security would risk making the user experience more hostile for little benifit.

(Talking about iOS here, but I’m sure it is similar on Android)