I don't know who is this people that you are talking about, but if it was the case, everyone would only use taxis already. Even if robotaxis would make the ride "half price", that would still be costly for a lot of persons, especially the one using their cars a lot.
Also you might like to own your car, to fit it to your need and style, you might need to use it to store items for period of times, you might want to be able to take your time, load and unload in private spaces, you might want to be 100% sure to have your car ready at the place that you want at the exact time and schedule that you need it, you might need your car for lot of small trips in a row without a clearly defined schedule, ...
Hi! one of those people! Live in a city with adequate public transportation that I never learn to drive and would like not to for as long as possible. To get to places I pretty much use uber for places that would take a while to reach with public transportation.
I think this is wrong. i think Musk is right about this.
People don't want to or cannot drive, people don't want to find public transport, people just want to get where they are going as cheaply as possible.
Robotaxis have to be cheaper than normal taxis with a person driving and charging wages.