Because you are now more dependent on private cars for transport.
Why would you use this instead of a system where you take a neighborhood bus to the local transit station & shopping center where you can pick up a light rail to the closest subway station, where you take the express train downtown to the high-speed rail station, where you take that to visit the next state for the day? No cars, and you can sit and read a book or take a nap or enjoy the view if you wanted to.
The only scalable transit solution is mass public transit. The world can't afford to pave a private luxury road for everyone to go wherever they want to go. They need to learn to sit next to random strangers on the subway or the bus. If people can't sit next to random strangers on the subway or on the bus, they should be seen as dysfunctional and sociopathic.
This really is one of the worst things I've seen. It may possibly be worse than his Hyperloop, another truly awful idea.
Elon Musk strikes me as one of those guys that defunds mass transit, and then wonders why mass transit is so bad. "It's always breaking down and never on time hurr durr.. So, therefore, buy one of my shiny new cars!"
He really hates mass transit for some reason. Maybe he just can't stand the general public? Is that why he's so into Mars, because he hates everyone here?
We need less pampered and coddled people like Musk, and more people with grit that has the ability to interact with the general public.