I have an enterprise account and they added this button today. Guess what used to be there? The profile image where you could so conveniently swipe up or down to switch between gmail accounts. This is the kind of UI garbage that makes you want to move your entire company to another service just because you can.
Yeah I used to go in the menu and click the other accounts one at a time until a friend showed me. Its this and removing the youtube click to add to queue popup that drive me bananas. They both worked so well why would you change it?