Yes, but you're still distracted, and that's the problem.

The obvious difference between a phone call and a conversation had with someone in the car is that the person in the car is also placing their life at risk. Unlike the person who isn't there, they can (a) see and (b) intervene when you're starting to drive like an idiot.

It's not that a live conversation is any less distracting. It's just that it comes with a built in safety mechanism.