Believe it or not, you pay for that haircut at basic training/boot camp and every other haircut you receive in the military. Perhaps the short haircuts in wartime Japan were for ease of wearing gas masks.
Naw! Not buying that. Women didn't have buzzcuts but I think gass masks would fit them. BTW, contrary to myth, a gas mask should seal even on a bearded face. I use a dive mask with no problem and I have a full beard.
All of the above, plus the conformity factor. The Japanese soldier was a useful tool of the Command-and-control society that was Imperial Japan, and the ease of removal or pulling on of gas masks, the ease of maintenance, and the lice factors were all contributing reasons.
Also, it made the first impression of sameness of all the Japanese soldiers that much stronger, that the slain somehow rose up again and kept coming at the GIs.
Yep. They don’t issue you much in boot camp that you don’t pay for.