For the average person in Dallas the car they already own is faster than waymo: it is sitting in their driveway where they left it (or in the parking spot where they left it - while cars are stolen that is rare enough to ignore). They don't need to summon it and wait for it to show up - which saves a lot of time. Those who drive used cars (which is most people) the car is cheaper than waymo as well.
My impression is Waymo is used as taxi replacements: people who normally take transit but there is one trip that it won't work for; or travelers who don't live there and don't want to rent a car; or people who plan to drink. They make perfect sense to anyone in Dallas for these reasons. However nobody is planning on giving up their own car and it doesn't make sense for them to do that.
Working transit would be a paradigm shift of course.
