It was World War One. When soldiers came back from service, they had short hair and were clean-shaven. WW2 and the Korean War reinforced this severe look even more. The hippy thing was a rebellion against the military establishment foremost.An older sister told me that it was because of the hippies that they started the no beard thing. As I began to find photos of older JWs I quickly realized that it went a lot farther back than that. Unless anyone can prove otherwise I would guess it goes back to Rutherford.