I think it's because of the shutter. The camera is capturing the image over a period of time so the photons for those trails will be additive.

It certainly does have that effect, but you're right in that it's not quite that pronounced.

I spent a lot of time playing Asteroids in the arcade growing up (that and Tempest). I have a physical problem with my left hand so I found playing a lot of later arcade games that required a lot of very specific movements of the joystick difficult so I kept coming back to those two because the left hand control was basically just a dial.