Science fiction was getting a huge boost at the time. Star Wars was released the year before. Battlestar Galactica started in 78. Invasion of the Body Snatchers, the Donald Sutherland/Jeff Goldblum one, was also 78. Alien would also come out in 79. Video consoles were being billed as super advanced and futuristic. I'm sure this came from that. What's interesting is that 8 years later, we got Arkanoid, a breakout game actually set in space.