The economies of scale of running a large scale operation would make it much more likely to reap a profit worth pursuing. In addition, there's no way Tesla wouldn't be directly impacted by the reputation of a fleet of privately owned vehicles running their software but in various states of repair and cleanliness. If it's actually the panacea for local transportation it's sometimes made out to be, it'd make no sense for Tesla not to run it themselves and have full control.
