Have you ever wondered why?

So you don't think I'm totally strange and think about random stuff all the time, there is actually a book out there with this title, so I got interested. And here is some more useless stuff for you!

Why do men have nipples?

http://www.straightdope.com/classics/a1_093.html
To tell you the truth, nobody really knows. The best explanation I've been able to find (and frankly it doesn't explain very much) is that nipples aren't a sex-linked characteristic. In other words, nipples are just one of those sexually neutral pieces of equipment, like arms or brains, that humans get regardless of sex. As you may know, every human being gets a unique set of 23 pairs of chromosomes at conception. These fall into two categories. One pair of chromosomes determines sex--the XX combination means you become female, the XY combination means you become male. The other 22 pairs, the non-sex chromosomes (they're called autosomes), supply what we might call the standard equipment that all humans get. These 22 pairs constitute an all-purpose genetic blueprint that in effect is programmed for either maleness or femaleness by the sex chromosomes. The programming is done by the hormones secreted by the sex glands. For example, the autosomes give you a voice box, while the sex hormones determine whether it's going to be a deep male voice or a high female voice. Similarly, the autosomes give you nipples, and the sex hormones determine whether said nipples are going to be functioning (in females) or not (in males).One interesting consequence of the developmental set-up just described is that during the very early stages of fetal life, before the sex hormones have had a chance to do their stuff, all humans are basically bisexual. Among other things, you have two sets of primitive plumbing--one male, one female. Only one set develops into a mature urogenital system, but you retain traces of the other for the rest of your life.It's tempting, therefore, to say that male nipples are yet another vestige of your carefree bisexual youth. Trouble is, male nipples are hardly vestigial. They're full-sized and fully equipped with blood vessels, nerves, and all the usual appurtenances of functioning organs. Why this should be so nobody knows--in some other mammals, such as rats and mice, male nipple development is completely suppressed by the male sex hormones. (Incidentally, don't start thinking that at one time our human male ancestors must have suckled their young. So far as anybody knows, male lactation has never developed in any mammalian species.)Human nipples appear in the third or fourth week of development, well before the sex characteristics. (The sex hormones start to assert themselves at seven weeks.) As many as seven pairs of nipples are arranged along either side of a "milk line," a ridge of skin that runs from the upper chest to the navel. Normally only one pair amounts to anything, but on about one baby in a hundred you can detect some vestige of the other ones, usually on the order of a freckle. There are cases of women who ended up with an extra breast, which made them freak show candidates not so many years ago. Luckily today the women can avail themselves of corrective surgery while the rest of us can watch Jenny Jones.
Pretty strange but once you hear that question you are like, yeah why do they. There are so many other things that make you go hmmm, but for now this is all you get. Maybe next week I'll think of some others for you, I know you are all dying to know.