AMP makes pages fast by forcing you to drop all the website fluff. Most will argue that fluff is not needed on mobile sites (I agree)... but try telling your client that.
Well, if you include in your discussion that most internet traffic is now mobile, and mobile users want quick access, and Google is giving them a way to distinguish whether you site will likely be quick (AMPed) or possibly not, and it may be in their best interest to signal to users that they provide a good mobile experience, it might go smoother.
