The Obvious UI Is Often the Best UI
Kind of funny that this is written by Google, responsible for some of the strangest UX decisions. Just look at Gmail. In the single email view there are 5 different toolbars, at different levels of hierarchy. Why is forward at one level, but archive at another? Why are there two sets of drop down menus? Maps is another disaster. Watching my relatively non-technical partner attempt to navigate Maps is quite eye-opening - different panes sliding in and out, Navigation, Places and Maps often conceptually colliding with each other leading to all sorts of confusion (unless you're very familiar with the Google suite of products).