Similarly, I had been trying to understand the value/benefit to add a SIM card to the vehicle or paying for ATT subscription after trial period. If you turn the hotspot on your phone on and connect your car to that, it serves the same purpose. The only downside is a slightly quicker discharge of your phone battery.
As an aside, my dealer visited me yesterday, it was 2 weeks after taking delivery. While not planned, for me, the timing was perfect. He was extremely knowledgeable. Issues I did not understand he answered flawlessly. I had a handle on most things but some were a mystery. Without a doubt, the best element of the dealer experience thus far.