Video games, largely, were created originally by people with psych degrees and programming/comp-sci degrees teaming up - especially online games. In the case of Verant Interactive, who created EverQuest, the original dev team was made up of people with just those degrees initially. So even back before freemium was a model, psychology was at play in games, though not nearly to the degree it's being employed today. No one I ever met working at SOE from the original EQ team was at all into the kind of things the modern game market is using - while they wanted people to be engaged with their games, they truly wanted people to enjoy their work; the addiction thing was horrifying to them, and made them wonder if they'd done too good of work on immersive techniques (much like some of the people from Facebook and other social media are now "out" of social media).