The plan for this is likely that it really takes off once self driving cars become the norm. When people are no longer required to pay attention to the road dur

The plan for this is likely that it really takes off once self driving cars become the norm. When people are no longer required to pay attention to the road during their commute, they've got much more time to become consumers. GM wants to profit from this consumerist time as much as they can by having an in car marketplace to compete with you phones/tablets. This doesn't make much sense for cars that aren't self driving, it's just about getting it to market asap.