I use it to check that the car is charging when it should be, and to see when it's supposed to finish. If I'm at home then I can see, if it's not going to have time to finish balancing before the end of the cheap rate tariff and give it some more time.
On one occasion I was on a Tesla charger and eating my evening meal, and the damn charge dropped. I saw this on my phone and was able to run to the charger and re-start it. If I hadn't seen that on the phone I'd have been in for who knows what overstay fees. (Although to be fair I think I could have got the same info from the Tesla app.)
I also use it in very cold weather to heat the battery and pre-heat the cabin.