People who hang arms of the window, why?

It's summer and I notice a lot of people out on roads with arms out the window like this: http://ift.tt/2vjEI8z's both drivers and passengers. Imo this is pretty dangerous since even a minor crash can damage your limbs. I also live in nyc so there's a lot of cars and sometimes spaces/roads are kind of tight. via /r/cars http://ift.tt/2wcu1RK