Here's a fun conspiracy theory proposed entirely in jest: Apple doesn't want to patch zero-days used by US authorities in order to alleviate pressure on its encryption practices. So they really only want to fix zero-days that are known broadly or get media attention. And they don't want to give too much incentive to researchers to report zero-days to Apple instead of selling them to the highest bidder (which may ulti…
Apple is not that different from the status quo on end to end encryption as to necessitate a conspiracy (probably even in jest ). They have no icloud encryption, no photos encryption, no device backup encryption etc etc.