No one ever explained "why" but I'm sure it began with a Puritanical philosophy of cleanliness next to Godliness

Hah, in university a whole bunch of us Indie types used to, I'm not sure why we started??? We were probably drunk!

We retain armpit hair for the singular purpose of retaining odour. The armpits are one of the two locations on the body (the other being the feet) where sexual pheromones are released to attract nearby potential breeding partners. There have been studies done which show the majority of women are able to identify their mates by the smell of their armpit sweat alone, which is unique to each individual. And like the feet, the armpits are often sexualized, with armpit-licking a very common sexual paraphilia. My suspicion is that the shaving of female armpits may be related to the cultural oppression of female sexuality. Shaving of the armpits not only reduces the amount of sexual pheromone the armpits can retain (and thus reduces the level of arousal it can instigate in potential nearby mates), but essentially infantilizes the woman the same way shaving of the groin does. At least on an unconscious level, shaving of the armpits says, "This woman is not a sexual being; she does not have sexual needs, and does not desire intercourse." In many parts of Europe, where female sexuality (and sexuality in general) is more openly acknowledged, it is common for women to keep their armpit hair. It is in Asia and North America, where women are supposed to be delicate, fragile objects to be coddled and protected, and who are too soft and sensitive to have sexual needs of their own, that armpit shaving is nearly universal.

Uh, hey, we don't do bikini waxing either...got a problem with that, too? :-)

Only women know that.