Yes, my in-built navigation system requires me to tether my phone to receive traffic updates. No tethering, no traffic updates or traffic camera alerts.

I don't have an alternative solution and understand a data connection is required for this functionality to work.

My point was that already I lose this service if I travel out of my own country and turn the data connection off to save money. If the car only had "a screen and a few buttons", relying on the phone for everything, much more functionality could become hamstrung without a data connection. I appreciate there are offline mapping solutions, but there are probably other service edge cases I haven't considered.