It depends on how you define London. Kingston, Sutton, Croydon are all part of London for example, but are not served by the Tube (although they have decent rail and bus links). If you live in Kingston etc you are more likely to have a car to drive out of London, and if you live in the outskirts of Surrey you may well drive to Croydon or Kingston or similar to do your shopping because you don't have great transport links to get there.
For example to get to Kingston town centre from where I live takes about 20 mins in the car but 47 to 55 minutes by bus and the two available busses run once per hour. To go by Rail I'd have to walk for 40 minutes to the station then take a train to Wimbledon, followed by a train to Kingston which would take 40 minutes.