Because rather than fixing the problem, you think we can avoid it entirely with a completely unreasonable elimination of cars.
Traffic exists because people are inefficient drivers. Congestion happens everywhere people live in sufficient densities, and it’s not the density you’re imagining.
Fully automated driving is also unlikely to happen in our lifetimes, because people like driving. But it could happen eventually, because the variety of benefits over other forms of transportation. One of those benefits is reducing traffic.