So it turns out that not only is email not secure, the stakes are very high when an entire account gets compromised.
Hacks generally happen a few ways. Your password can be guessed, or a flaw in your software can be found, or someone can be induced to take action that will enable one of the other two options. Flaws in software are often misconfigurations, but often their are coding errors that can be exploited as well. These are too-common occurrences.
Keep in mind that we are looking at tens of millions of lines of code. How would you code audit, for example, Microsoft Windows? Even worse, industry will not stop them because industry is trapped in a business model that requires it to constantly publish updates, all of which add more code. Consumers will pay for software only if it comes with support, and that is signaled by constant updates, and those are only cost-effective when done by legions of low-cost entry-level programmers. Enter the perfect loop for hackers.
At this point, people with important jobs or anything to hide are making the calculus: how destroyed would I be, if all of this information were released to the public? The answer is that for all of them, the damage would be so vast that it cannot be risked.
Look for more paper letters in the future. Email has died.