AT&T Connected Car Unlimited Plan Wi-fi in your vehicle for an extra $20 a month, 'if' you are a current wireless customers and 'if' your vehicle meets the requirements e.g.year and model of vehicle and lots of other small print 'if' you're interested. Unfortunately, my vehicle doesn't.
I have no need for it , either. Since my phone is cellular, I can connect anytime with that, and I rarely even use the phone when I am in the vehicle. I can see that someone who drove a lot and wanted to connect to some program with Wifi might use that; but the pickup we drive (belongs to my daughter) is set up that the radio automatically connects with my phone. I really don’t like that, because when I do get a phone call, it blares over the radio speakers, and I would rather just answer with the Apple Watch instead.
My phone is connected to my car and it's great because the reception is much better in the car. I rarely(once in a blue moon) use the phone as a phone when I'm not in the car because reception is horrible.
I thought this was interesting. Other than what @Yvonne Smith mentioned I can't see any reason to get this especially if you are a wireless customer of AT&T. It would be redundant.