They aren't replacing taxis, they are replacing cars.
Unless you want to own a specific speciality car (Ferrari, Jeep, etc), Waymo eliminates the need for you to buy one. It's Uber but without the overhead of paying a person, which means price could normalize so close to the actual operating expenses of the vehicle that it just doesn't make financial sense to use anything else.
That study doesn't seem terribly relevant. It concludes that owning a vehicle is important to people right now. It doesn't seem unreasonable to assume that in the future, cheap and ubiquitous ride sharing options could pretty quickly drive those percentages down.
Unless you want to own a specific speciality car (Ferrari, Jeep, etc), Waymo eliminates the need for you to buy one. It's Uber but without the overhead of paying a person, which means price could normalize so close to the actual operating expenses of the vehicle that it just doesn't make financial sense to use anything else.