Let's ignore the maps; pretend they never existed. I can drive wherever I want, but my time is limited. A child's time is less limited, but their location is more limited. A college student might be a mix of the two: mobile, with some significant free time. Another variable: location. In a rural location, there might not be a pokestop within several miles. In an urban location, there might be three within range of your home's family room.
From my perspective, people are already playing a bunch of different games, based on available time, mobility, location, and density of other nearby players.