Ahh, I'm an outlier then. One of my ex's used to do it to tease me, with no provocation on my part, it was just something she started doing one day. Wicked girl. Between that and another girl noticing that I was looking -- and very, very showingly increasing her movements, plus talking about me noticing a few months after -- it is difficult for me to imagine another scenario, haha. Stupid life experiences.
I don't believe most people are doing it with any sort of intent, at least initially, but, well, I've experienced the other side, so I certainly can't say it doesn't happen.