A couple of weeks ago, waiting for my luggage at Oakland Airport, two thirtysomething young women visiting from L.A. asked me how to get to downtown SF. For about $6 each, I said, they could take a shuttle bus to the BART train and be downtown in about 30 minutes, and since I was going that way anyhow, I offered to help guide them there.
As we paid the bus fare, one of them enthusiastically said "Wow, this is cool! I've never been on a bus before!"
After they got off the train, I began trying to reconstruct a life path in which someone would never have been on a bus. I wasn't able to do it.