I have some good news for you. We have actually added this feature recently on Tableau Public. There is a blog posting here detailing this change Maps Get New Zoom Controls | Tableau Public . As the blog states, we'll be making this change across Tableau Desktop and all of other clients with the 9.0 release.
Such good news! I've published a few things from Tableau public and they've all got the new zoom control features already, very pleased about that!
Thanks for the heads up,