It's probably more fads and fashion than anything else, with some periods in recent history and certain places being conformist, others anything but.
No doubt you've seen the images on the plaques attached to two of the space missions depicting a man and a woman, both nude. The first one, Pioneer 10, was launched in 1972, 46 years ago. They have what might be described as contemporary hair styles, though no body hair is depicted. What would they look like if designed today, do you suppose? Would they even be nude? If they were designed in 1900, the hair styles would at least be different. The man would invariably have a mustache. Thirty years earlier, he'd have a beard.
In the 1950s, having a beard was not done. A mustache would be a pencil-thin style. I even remember a line from a movie, "Why are you hiding behind that beard?" (The character said he grew it to look older.) Any style that teenagers favor is usually considered rebellious if it isn't exactly like their parents, who of course, went through the same stages. It is ironic that as your body hair increases, the hair on your head sometimes begins to thin out. Women don't have the same hair issues. They don't have mustaches, except for the occasional aunt.
