Just like they, and Microsoft, and many hardware manufacturers, also know every banking password/legal document/medical data in the world. Closed operating systems, applications, drivers, can all be used to exfiltrate data unbeknownst to users, including administrators. We're forced to give them some trust, otherwise the only choice would be to use only systems, software, hardware that is completely open down to the last bit, which sadly don't exist as a whole.
This sort of ideological take is lacking necessary nuance is and ultimately thought-terminating. There’s a difference between trust and concrete proof that something is happening, and there are degrees of both. Information security is somehow a justified field despite the fact that only a very small handful of shops own the full stack. It’s all about understanding and mitigating risk.
I don't disagree in principle but let's not conflate the trust required for proprietary software with the trust required for a service that is known to exfiltrate your data.
I may have read too much science fiction, but the mere fact that someone has full access to all my data worries me, if not because we don't know anything about which form of government we would have in, say, 10 years, and how easily a corrupt government could force those businesses to surrender that data in order to find their "enemies".
BTW, I don't live under a rock, I do online banking from the PC and have pretty much given up telling my lawyer and doctor not to use Whatsapp to send and receive sensitive documents, then keep them in their unencrypted phones, but that doesn't prevent me to be worried by how easy it has become to obtain personal data about someone for those who can.
