I don't know why this still surprises people, or why Google is being singled out here. Information is transmitted by copying. Every provider has to look at and analyze your messages if they want to do clever things to them, like let you search your archived mail server-side. Even if they don't do anything with your messages themselves, they're still compelled by the government to parse through it all. Nothing is safe.

Whenever anyone asks me to explain how the Internet works, I don't talk about tubes or connected servers, because thinking your message is "in" a pipe is a broken abstraction; it makes people imagine nothing sees or touches your messages until they arrive at the destination. Instead, the mental model I encourage people to have for Internet is that "each packet is like a message stuck to a big public message board." Privacy is not the default; it's a public system, and privacy is something you have to actively create on top of it (via encryption, onion-routing, etc.)