You often see histograms where the vertical scale does not start at zero. The problem with this is that it distorts the appearance of the data.
Suppose this had been the data
Then this would be the histogram
Now redraw with the vertical scale starting at 10.
Now, for example, you can see the class 10.5 - 17.5 looks four times as big as the class 3.5 - 10.5, whereas in reality it is only twice as big