Even though email has evolved a lot, it still registers as a more personal 1-on-1 channel so that's the vibe we expect. Yet a lot of the advice for it are adopted from formal writing and marketing messages.
To put this in perspective, you know those viral TED talks? Yes, they sound amazing and inspirational delivered in front of an audience but if someone started speaking like this to you 1-on-1? "Uh brb, I need to go to the washroom."
For emails, marketing speak (talking about benefits, mentioning your results) and corporate jargon can sound completely out of place. Even if it's "good copy" or "sounds professional".
Art of Emails email templates show someone what's in it for them or what you can do for them like you're chatting them up in person. So they're much more likely to reply.