People like to think that they can rely the sender address as an unspoofable source of truth, and do not understand that the message is just a text file, and you can make it say anything you want.
No one inspects the delivery servers or the message routing, and even that can be sufficiently obfuscated.
Using too-big-to-fail services like gmail, that attempt to provide analysis and alert you to suspicious patterns is nice, but it doesn't solve for the actual realities of handling email. Furthermore, if there were one email ring to rule them all, we'd be haunted by a more ominous problem.
Still, the level of confusion and misperception about common technology, and what is and is not possible, is clearly as big a problem on its own. It sucks that people are left with such superstitious paranoia, because they don't understand how naked they actually are.