Derived from the compulsion to dedicate inordinate amounts of time to one or more of the game's voluntary missions: making friends, writing them letters and sending them ugly clothes, expanding your house, paying off your mortgage and expanding your house again, collecting all the furniture in a set, fishing, donating fossils to the museum, building a second town, planting fruit trees, getting iglooed, hitting unwanted neighbors with a butterfly net...
Mel: Gotta play Animal Crack. Haven't seen the exotic bed yet.