Any source for that “Apple just doesn’t care”, as opposed to thinking there are security/privacy tradeoffs or other considerations that cut against such a feature?
If Apple can store the sms/iMessage, and email history, and health/journal history, and my Wallet payment history, in a safe manner I would think Apple can store notification history in a safe manner. How would notifications be meaningfully different from these?
I think the proof of Apple’s level of care is in their lack of attention to this issue.
With modern cryptography techniques, Apple could certainly do it if they cared enough. I guess the potential benefit doesn't justify the potential effort and cost related to the change, from Apple management point of view.