Games had just started out with the release of Pong and as time went on, new games were designed and new developers arose, A lot of testing happened in the early days to see what worked and what didn't; to see how much they could push the boundaries, hardware started to develop faster and a market was created for games, then in this period of time, games found a nice middle ground that settled for the hardware they had at the time but also pushed forward a little bit later to make better games, from 8 bit to 16 bit and so on.
Many games had patterns and could be predicted once practiced enough, this gave an immersive and competitive feel to the games as they became addictive, the player learned and quickly strategised each go the player had. Especially with a score system, everyone competed to be the best.