I have significant doubts about this "any Tesla as robotaxi" idea at least if you're referring to Musk's empty promises about how you could make money off your own Tesla while not using it.
Oh man, I have serious doubts about that! But that's what they've claimed they want to do. And I can see the profit motive there, so I have no doubt they'll try. I'm not saying it'll work.
You're missing the point, nobody is talking about trusting these companies.
You can tell if a connection is encrypted end to end or not. And if your paying for that service you can sue if you aren't receiving what your paying for.
In digital security nobody relies on trust if they can help it. And security matters if you want to keep a competitive edge on your competition, so even shitty companies care about that.