Keys are managed by the government.
Though it hardly matters when ~90% of iPhone users likely have iCloud Backup on. In which case their messages will be backed up to the cloud to where the government could get keys.
If you don’t know apple turned over private text messages of congressional officials and NYTimes reporters WITHOUT protest or question to the Trump Administration. And before you say otherwise Google and Microsoft both did not.
They do not care about privacy, it’s all marketing.