It's also annoying to have the amp menu bar taking up space at the top. Screen real estate is scarce and another menu bar at the top is just confusing.
Since AMP uses an overflow technique to handle content/scrolling, the page never triggers a scroll event on the body. So not only do you see a toolbar at the top (which admittedly, slides out when you scroll down), you see the browser toolbar at the bottom (which persists!)