In a society where "everyone" is having and using a car, setting up free buses to attract potential shoppers probably doesn't make economic sense. Here in Oslo quite many "ordinary people" realize they don't need a car, hence the potential users of the free bus ofer represent quite some purchasing power.

At the other hand ... while the single fare tickets for the transport here is reasonably expensive, monthly unlimited passes are comparably cheap, so almost all public transport uses have "free transport" anyway.