A taxi has many of the listed benefits;
- you don't need to buy the car - you don't need to drive the car - it's available on demand through your phone - the utilisation of cars is very high
So what is the functional difference between a shared-ownership, driverless car, and a standard human-driven taxi?
You see a lot more taxis in cities with lower human labour costs (such as Lima), or where the cost of parking outweighs the cost of the driver (such as Manhattan).
Don't underestimate the price difference. It's one of those things where a large enough quantitative difference becomes a qualitative difference.
In the US it costs around $15-$20/hour to hire a taxi driver (median wage is $11.20 per hour). Over the course of a month (24/7) that starts to approach the cost of the car. Granted, the taxi isn't used 24/7, but the operator still has to recoup the cost of having it available all the time. I wouldn't be surprised if about 90% of the cost of a taxi is due to employing the driver.
Even if all you do is reduce the cost of a trip by a factor of ten, you're going to see big changes.