the default is weak because it's the most user-friendly option. Otherwise, you end up with edge cases where the user lost their only device, or they forgot their password, or ... the list goes on and on, and they lose all their previous chat data.

That's a very user-unfriendly place to be. Most users won't understand why their data is gone, become unhappy, and distrust their devices to safely store their data. It's not even about buying more Apple products at that point - it's just literally reinforcing the stigma that "I can't understand tech, it's too complex".

You can't be security-maxxing and user-experience-maxxing at the same time. I do like Apple's approach which at least gives you the option.