Used to be able to shut off wifi and leave it off. Had it off for years.
Sometime fairly recently, seems Tesla made a change so that turning wifi off is not sticky. It turns itself back on next drive. Even says so on the dialog for turning it off. Hmph..
I kinda hate this because it seems now when I'm driving and stopping near places with wifi broadcasting, the car will sometimes ditch the cellular connection (turn it off) as it attempts to login to some wifi off the street. Driving away to open road (no wifi around) brings cellular back, usually. Today it didn't. I had a knocked out internet for most of the whole ride... only a glimmer of internet enough to do one "nav" and get a blue line... then dark again.
I guess the hope being that while parked near a pre-authenticated wifi, like your home.. the car will use your bandwidth instead of Tesla cellular. This must be some meager way of Tesla trying to bring down cellular network costs.