IT WAS EASY TO SCOFF at grown men sporting 2014’s “urban lumberjack” look—the sort of generously hirsute Paul Bunyan-type who held a 9-to-5 graphic design gig in Portland instead of an ax. But even though the vogue for plaid has waned, beards have persisted, said Wayne Wildrick of Fellow Barber in Brooklyn. “It’s a generational thing.” He believes clean-shaven faces, like buzz cuts and flat-top haircuts, are relics of yesteryear.

With the currency of beards came a multibillion-dollar industry dedicated to ensuring that men’s...