The reason people wear wristwatches is because of World War I
The wristwatch wasn't created by the military but it certainly brought it into the mainstream.
That's what an interesting article at BoingBoing explains of the timepiece that was popularized during World War I. At the time, most men used pocket watches, while women tended toward wristwatches (sometimes called "wristlets"). That changed during the bloody four-year conflict that began in 1914.
Linda Rodriguez writes:
It would take a global war to catapult the wristwatch onto the arms of men the world over. Though the wristwatch wasn't exactly invented for World War I, it was during this era that it evolved from a useful but fringe piece of military kit to a nearly universal necessity. So why this war? Firstly, the development of the wristwatch was hastened by the style of warfare that soon became symbolic of the First World War: The trenches.
"The problem with the pocket watch is that you have to hold it," explained Doyle. That wasn't going to work for the officer at the Western Front – when an officer lead his men "over the top", leaving the relative safety of the trenches for the pock-marked no man's land in between and very possible death, he had his gun in one hand and his whistle in the other. "You haven't got another hand in which to hold your watch."
Not surprisingly, the transitional pocket watches-turned-wrist watches were given a much more manly name: The "Trench Watch." And when troops returned from the battlefield, they brought their watches with them, thus popularizing the wristwatch and relegating the pocket watch as a thing of the past.
"When these war heroes were seen wearing them, the public's perception quickly changed, and wristwatches were no longer deemed as feminine," John Brozek wrote in International Watch Magazine. "After all, no one would dare consider these brave men as being anything but."
So if you're checking out one of those new, high-tech Apple Watches, don't thank Tim Cook. Thank a World War I doughboy.