They can travel more simply because the cost of time spent in travel is now reduced. I think cars will be fundamentally redesigned where it functions as a mobile office, with a TV/Computer screen and a place you can sleep.
If I wanted say to go to the beach for the weekend and I live say 7 hours from the beach, it’s a huge hassel for me so I probably do it once or twice a year.
But with driverless cars I can get in the car every friday night, and by the time I wake up in the morning on Sat I’m at the beach, and I can spend 2 days there and depart on Sunday night, and by Monday morning I’m back at home ready for a trip to the showers and show up at work.
The cost of travel time would be reduced to almost zero, and encourage people to actually live more spread out rather than squeezed together in cities.
If we ever get to the point where you can sleep comfortably in a car or have an office in a car, then you might be on to something. Personally, I think such a vehicle would be so prohibitively expensive that it would likely end up losing out to an interesting innovative Uber-like service with mobile "RV/motel" vehicles that can accommodate 12-15 passengers making on-demand trips in tour buses that have a wide range of amenities for passengers.