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, ...