One large potential security benefit is being able to know and report the real-time positioning of cars. This could be then used for responding to emergencies or more broadly tracking suspects or wanted individuals.
Or selling the data to repo agencies. Or tracking someone down over an unpaid parking ticket, past-due water bill, or who knows what else.
I didn't love the OnStar system in my GM vehicle, due to the ability for misuse, but was kind of OK with it because it was the vehicle manufacturer, not a government agency. Not a fan of installing any kind of device with live-tracking capabilities that is administered by fed/state/local governments.