It makes more sense for self-driving cars. If they get confused and just stop or pull over, you can have a technician remote in and drive it back to a depot or just get it unstuck.
If you're running them as a taxi service (which I think all the major self-driving companies except Tesla are), you need a way to get stats on the fleet and to direct a car to go pick someone up.
As of now, taxi services seem to be the focus of the self-driving industry because the LIDAR hardware (among a couple other things) is too pricey for consumers to justify owning. That's going to require some way to communicate with the cars. Cellular data seems a reasonable way to do that. I don't see a remarkable advantage over building their own boutique network of transmitters just to say they aren't technically on the internet.
If you're running them as a taxi service (which I think all the major self-driving companies except Tesla are), you need a way to get stats on the fleet and to direct a car to go pick someone up.
As of now, taxi services seem to be the focus of the self-driving industry because the LIDAR hardware (among a couple other things) is too pricey for consumers to justify owning. That's going to require some way to communicate with the cars. Cellular data seems a reasonable way to do that. I don't see a remarkable advantage over building their own boutique network of transmitters just to say they aren't technically on the internet.