I wouldn't even say it's a challenge to talk to strangers. I can do it fine, and do it all day at my job. It's just, I don't feel the desire to do so simply for the sake of doing it. If I'm sat in a park reading a book on a Saturday morning, I can pretty much guarantee you I do not want to talk to people, yet you'll get people who just want to plop down next to you on the bench, let out a sigh and say "Hoo, boy what a week, eh?," and expect you to put down what you were doing to keep the conversation going.

Think about this. When they made the movie 'The Net' in 1995, they showed how oddball Sandra Bullock was by having her order food with her computer.

In that far off past, even if you were introverted, you couldn't function without doing almost all your transactions live and face-to-face.