The Single Shoe Phenomenon

I find myself perpelxed by this "Single Shoe Phenomenon". Have you ever been driving down the street/highway and come across a single shoe lying in the road. I find this astounding! I don't understand why it's always a single shoe! Where is the other shoe? How can someone not know that they have lost one of their shoes? Further more, as you're driving down the road, especially a highway, what on earth would you be doing inside the car that would ultimately result in the loss of one of your shoes? I have posed this question to a few people, one proposed theory is that the former owner of the lost shoe put their shoes on the roof or tailgate and forgot about them. But if that was the case, you would think that more often than not you would come across both shoes instead of just one! Another theory is that it's a lot easier to dangle one leg out of the window than two legs! In my experience, I find most of the single shoes to be tennis/running shoes, which would likely be tied and not likely to fall off. I also wonder what the owner of the now "split pair" of shoes does. Does the owner try to retrace their steps to retrieve the lost "soul"? Does the owner continue to look for days/weeks/months? At what point do you give up and throw away the remaining shoe? Or do you donate the remaining shoe and hope it finds it way to a good new home on a one legged person? I guess the point I'm trying to make is that maybe people shouldn't treat their shoes with such reckless abandonement.