Gotcha. I think it is related to this issue:
It seems the devs feel a back button in tabs is not so good an idea. Back button missing and History erased from tab view? · Issue #612 · ionic-team/ionic-framework · GitHub
However, I have already opened issue # 737 to ask to support it with left-buttons : Back / Left Buttons in Tabs · Issue #737 · ionic-team/ionic-framework · GitHub
LOL: The menu thing. I am so used to the menu icon on the left that I never noticed the one on the right.