Fashion Changed

"Perhaps the most remarkable is a coin with two obverses - that is, one side carries the head of Trajan and the other of Hadrian, both laureled. What was unpresciented was the latter's short-cut beard. Those who met him from day to day were familiar with this artful innovation; as he well knew, in civilian dress it made him look like a Greek, and when wearing armor, like a down-to-earth soldier. Until his assention, emperors's faces, whether in statuary or on coins, had been clean-shaven. Now the fashion changed: men in every corner of the empire looked at their money and discarded their razors."

Hadrian and the Triumph of Rome 
by Anthony Everitt