Tank 8 was released in September 1976. It is one of the first games at Atari to use a microprocessor to control the tanks. Previous tank games were all hardware only.
During attract, all the tanks would move and shoot at each other. Some smarts were put in the program to do this. However, when someone inserted a coin, all the tanks snapped back to their start location. ONLY paid tanks would play, others would sit in their start positions and do nothing during the actual game. This meant that one person playing alone could not do much, and you really need more players for this to be fun. It seems that marketing discovered that when computer player tanks moved, players THOUGHT they were playing without ever inserting any money, so they decided to stop that from happening.
The executives at Atari use to come into our lab at lunch time and watch this game play its attract mode. The tanks would move about for several minutes using random attack programs, and the winning tank was always different. What they were actually doing was placing bets on the different tanks and wagering over the winner.