I connect I Phones to the USB ports. As you said the phones charge when plugged in. But they also connect apps on the phone to the car. For example I use it to stream Spotify. I also use it to listen to directions from Waze. So, it is more than just a charging connection.
For the car to recognize the phone you need to choose the phone icon in the car and connect the phone by naming it. The car will remember it. In my 2020 GLC the screen shows both Rob's phone and Donna's phone. So we need to tell the car which phone is connected. It takes a couple of clicks but it is easy to do. My daughter, who seldom drives the car, also plugs her I phone in when she drives the car. She uses it to display maps from some other app.