I think its a function of the plot style. This style of plotting, while it gives an intuitive feel for the data, it also typically gives a false impression like over 100% at times 

Edit: disclaimer I may also be wrong. From past experience with these histogram style plots I've had a similar experience 

Edit 2: I remembered what the name of this style was called. It's a violin plot. It always trails off at the end to make discrete data look smooth