Culture.
That’s the whole answer. You can find tribal societies in which only the men dance, and societies in which the whole family dance.
In western societies, women soon learn that they have the freedom to dance as a sexual signal, as **Daerlyn ** mentioned. (Probably why gay men have equal freedom to dance and why straight men are inhibited from doing so in some circumstances.)
It’s relatively recent as well. For much of the 19th century, women were barred from places were alcohol were served in the U.S. Men did dance to various kinds of music, from fiddling to accordion, but these were athletic dances that the clothing women wore wouldn’t accommodate. The cakewalk was a musical competition among blacks, in which they made elaborate moves seem easy, from the which the term “cakewalk” for an easy victory emerged.
Other dancing was more formal, usually in groups, such as reels or square dances, in which individual dancing would be meaningless.
You need to get into the 20th century before you even get to nightclubs where there was a special purpose to go to for dancing. Most bars still didn’t have that kind of music or floor room.
Jukeboxes helped launch dancing among teens. They were places in soda shops, where teens congregated after school to have ice cream and sandwiches. Girls would put on fast music and move their bodies. Couples dancing was still the norm, but girls would dance with each other if no boys would participate. Boys wouldn’t do this for fears of gay accusations.
Dancing just for the sake of moving a body to music hits with the rise of roadhouses after the auto became the norm. These sold illegal liquor during prohibition, illegal other substances after, allowed people to meet partners other than their spouses, and generally had bad reputations for depravity and sexual license. Speakeasies, and then nightclubs, in the city matched them. In the post-war era, music was faster and more of a norm, and moving one’s body to the music without formal dancing was a natural response. Clothing also changed so that women wore less clothing with less restrictiveness - try doing some modern dances in a girdle, stockings, and high heels.
But the whole culture **bucketybuck ** talks of is something so new for the mainstream that I’ve seen it develop in my lifetime. He may think it’s some kind of norm for the world, but it’s just the latest development in western societies, a mixture of sexual freedom, easy access to stimulants, casual dress, the fading of formal structure in dancing, and sexual freedom. Yep, it’s really all about sex.