Simple answer - The dawn of the video game. Blame Asteroids, Pacman, Frogger, Scramble, Breakout and Galaxian.
I vividly recall the last of the pinball containers consisted of Paragon, Space Invaders, KISS and a few others. This followed the previous container of Mata Haris, Globetrotters, Eight Balls etc etc .. (I still recall these days and consider myself to be very lucky)
The next container that didn't leave had the Fathoms, Medusas, Eight Ball Deluxes. When I asked my old man (ten years ago) he simply told me that he was buying videos by the container from Japan.
There were not distributors (as there are today) - especially in the 60's and 70's. Dad used to fly over to the Bally and Gottlieb factories and pick them off the line. Leisure and Allied used to import them in the mid seventies and some operators bought direct from them. Flyers were sent weekly - and I have many flyers with the actual price of the machines (new) and some second hand. I've retained all these flyers. I did have a thread on this in the Flyer section.
System one machines were rubbish (grounding issues) - so system 80's were avoided. It was either Bally or Stern. Williams system 6 were avoided as well. Many Operators simply bought Ballys and Sterns in the early 80s before the video age took over.
