I may not be qualified to write long post on this topic.
This is something from what I keep observing and how things are around me.
Music is a great company while running. Lot of runners like to plug in music and keep oneself motivated to run. Some keep the volume low while some keep the volume high. The genre of music also varies.
While the attention is to running and music, lot of them are not aware about what is around them. When we block the ears with music, we are blocking that essential sense from listening to approaching sounds form behind. Theory could be that run against the flow of traffic.
At least in India, the flow of traffic is not restricted to one side. There are lot of road uses who drive/ride their vehicles on the wrong side also. There are in this some elements who would extend their arm on to the runners. Though I have no idea whether extending the arm onto body of runners translates to climax. It is definitely going to take decades to change the mindset of our people. In this time one cannot stop running citing these reasons.
When not listening to music we tend to listen to sounds around us and it is quite probable that we may move away from these elements.
If listening to music is something that cannot be avoided then it is better to run inside parks or around lakes where there are more public. Or to run in a group who also maintain same pace.
Run safe, be safe.