Bandwidth is often not the limiting factor on mobile networks. AMP reduces the number of TCP connections your browser has to open (each of which requires 2 RTTs, and many of which will have HTTPS running over them which requires another one or two RTTs).
Take all those connections and introduce a 1-5% packet loss rate, and suddenly there's a very good chance that any given "page load" (really dozens of requests) takes perceptually "forever". That is what AMP helps with.
Take all those connections and introduce a 1-5% packet loss rate, and suddenly there's a very good chance that any given "page load" (really dozens of requests) takes perceptually "forever". That is what AMP helps with.