No, it has to do with context. In an email you will frequently have to provide more context for your answers to make sense. Chat is a conversation, which search drops you straight into, may with AI you could get placed at an appropriate starting point, but you're still reading a conversation. It's much easier to get dropped into a correspondence. To me the difference is like reading someones letter, vs. overhearing a conversation in a bus.

This obvious assumes that who ever wrote the email isn't a madman, who insist on using emails like it was a chat.