Public Transport

Bus drivers are expensive. If you can remove the cost of the driver your typical transit system can run 1/3rd more service to the people. Run more service and your transit system becomes more useful - either you increase coverage and so people can get more places thus they don't need a car, or you run more service on the routes you have and so people don't think a car is more convenient than transit. Either way, this is a big win for people who are using transit as the system is better, and typically that level of service increase will attract people who currently are not using transit.

Of course there are likely costs of autonomous systems as well, and so likely you cannot add that much more service, but any more service is a large win.

It isn't that they don't want to pay these people it is that they cannot! Money doesn't grow on trees, drivers pay needs some come from someplace and that pot is limited. You can talk about increasing that pot, but even if you can do so it is still better to get more transit service.