It's twofold. One, they want some way to notify you back when your charge session is nearing completion, or if you get unplugged unexpectedly. Two, they want the data on your usage individually identified, so they can sell/mine it.
They really should just call your phone, I can't think of a single other long-wait activity that forces you to install spyware. Oil changes, doctor / dentist appointments, furniture delivery, etc. They all just give you a call
Many people don't want to give their SMS-capable number to a random charging station in another state. I don't mind giving my number to my doctor, but a charging station is a different risk profile.
Frankly I’d rather install an app on my iPhone than give the company my phone number. At least with an app I can deny location, contacts, and all other access.
To each their own! I can not stand having random apps installed on my phone. They all eventually turn into notification spamming spyware. I get spam phone calls all the time anyway, have the charging station call / text me and leave me a message instead