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Apple ALREADY provides a solution for the super paranoid ...
This is true, but it isn't just about being paranoid. Think about it this way. Apple says (in Jan 2019) they have 1.4 billion active iOS devices, and several hundred million Macs.
I suspect a huge percentage (99%+) store backups and/or at least use iCloud services for things like Safari history and the like. However, whether it is 50%, or 99%, the total number is between 700 million and 1.4 billion iOS devices, plus macOS. How are all these stored? On other servers, such as Azure, AWS etc. They are of course encrypted so are not much good right now, but the number of hacks we've seen and employees with access to the data is huge. All it would take is one employee to make a backup of all these or make a mistake and leave them accessible which has happened a large number of times. Or one employee to be blackmailed, or just click on a bad link ... . Then all the backups and search histories etc are out there somewhere. There are plenty of government agencies who could be doing it. USA, China, Russia, Australia, Canada, UK - many would like that kind of data.
After they are compromised, all it takes is one person out of a somewhat large group with access to the keys at Apple to be compromised - criminal, blackmailed, stupidly clicking a link, huge payday, heart bleed or other software bug letting someone in etc - and then all those backups and histories are available. They don't have to occur simultaneously. The backups could've been compromised in 2015 or 2016 and just sit there until the key is compromised. 700 million to 1.4 billion is a huge target that would be worth a lot to the right people.
Contrarily, if you accomplish all of the above above, but only for one key individually, sure it would be bad for the one person compromised by losing their key, but it wouldn't be bad for the other 699.999999 million devices.
It isn't just being paranoid, it is thinking about how the ecosystem can be compromised and the consequences of having it happen.
A huge data breach would be terrible for everyone involved, and would devastate Apple's reputation for caring about privacy and consequently the stock price.
Just think about the number of CVEs for bugs each year and the number of security updates for all devices to close them and then all it takes is 1 to hit the wrong person and hundreds of millions of people lose their privacy.