Here's what Wikipedia has to say, which isn't much.I'm not sure when it started, but I personally thought that it may have been as far back as it was normal for a girl to be of marriageable age upon their sixteenth birthday and could thus be married off. But I haven't looked into whether that was ever true, so... But, considering the other things that I do know, I highly doubt that it was just for virginity's sake. It sounds more like they remained a virgin for a certain reason, and for a husband is not only likely and believable, but it has been done in many cultures through many ages.