I see.

Then perhaps you can explain why so much stuff leaks from, say, the USA government?

Not just the stuff from government employees or contractors like Snowden and Manning who appear to be motivated by whistleblowing, but also the actual double agents working for the Soviets in the Cold War, and the apparently accidental leaks of NSA spyware: https://en.wikipedia.org/wiki/EternalBlue

These are the typical use cases for key revocation yes? The key should not be installed on non suspected user devices anyway in my opinion.

Great, that just leaves the possibility that the system to install keys will itself be compromised, perhaps something like happened a few years ago with a downgrade attack to the old USA “export grade encryption” back when crypto was counted as a munition. The use of e2e encryption started to become a general standard in chat apps precisely because centralised keys proved to be a weak point after Snowden.

As for revocation: https://news.ycombinator.com/item?id=29642783

Snowden got a lot of data without anyone stopping him. The risk is what if he’d been malicious instead of a whistleblower?