The article states that the video conferencing feature would only be available for use when the vehicle is stopped. In other words, any time you were able to use it you would also be legally allowed to use a cell phone.
Then you'd have the issue of pairing your phone with the car, which for some cars isn't always obvious.
People who don't travel a lot often have phone plans with crappy coverage in random areas.
In short, if you want to ensure a reliable way for someone to contact a customer support person from the rental car company, relying on the users cellphone and hands-free setup is NOT the optimal case.
Of course a lot of travelers don't even have a valid phone. Especially foreign tourists.