Long story short: WW2

The military required men to be clean shaven, which was partly tactical (proper gas mask seals), partly to whitewash the service (e.g., black men can have severe skin reactions to shaving every day), and had other benefits to unit cohesion and general order (routine personal fitness and hygiene).

Well, that stuck, and an entire (massive) generation of men and their male children were taught that to be good they simply had to be clean shaven. Those two generations make up the vast majority of business and political power in the US, so the idea of “success” and “power” was idolized by a clean shaven male. This was further accentuated by the counter culture reaction of this cohort’s kids in the 60s and 70s, where longer and unkempt “bad” hair was cast against this “good” clean shaven look.

Fast forward to today, those traditions and appearances have been baked into most of modern life. As the boomer population starts to fade away, so will the tyranny of the razor.