AMP in email could, hypothetically, allow me to hit the "checkin to my flight" button for a Southwest flight directly from my confirmation email without having to bump over to their website. That's cool, convenient, and simplifies my life. It also benefits the corporation (their resource allocation is easier if they have a firm count of flyers) and it benefits Google (I'm more likely to use an email client that facilitates this).
The business world is full of win-wins, and this has the potential to be one of them.