The bar is back, but there aren't any settings to control it
The recent Google Maps redesign was great, but were you missing the measurement scale bar? Well it wasn't just you, and Google has apparently responded to some criticism and put the scale bar for measuring distances back in with this latest app update.
There aren't any settings to show or hide the bar, and it seems to only appear when you move the map or re-zoom to a new distance, then disappears quite quickly. We might have preferred if Google just gave an option to keep the bar on or off permanently, but beggars can't be choosers, we suppose.
Go grab the update from the Play Store link above. It seems to be pushing out widely right now.