But it's only good if you are going from one end of the tunnel to the other. You are cut off from all of the destinations in between. This is fine if you're talking about a tunnel that goes across a highway or something, but not great if you're bypassing all of downtown. I'd much rather see cars and trucks underground and bikes on the surface.

One could imagine a city where the streets are only for bikes/pedestrians/scooters/etc... and deliveries happen via underground tunnels where there is parking every other block and a freight elevator to bring the goods to the surface. A kind of futurist ideal that will never work because it would be horrendously expensive and the elevators would always be breaking down and as the city grew the system would be trapped at its current size and become increasingly overloaded over time.