Result: Today in the U.S. 150 million cell users (up fivefold since 1995) talk an average of eight hours a month (up fourfold) while paying a dime a minute (down by a factor of four).
That dynamic is a mix of roleplaying rules (levels, experience points, etc) with wait-or-pay rules (energy, building with clicks, paying to shortcut) and guided goals through a repetitive activity (digging, questing, item assemblage).