Or not. That seems like an awfully large generalization based on one city whose airport rail service hasn't had much time to establish itself.

Counter examples: In London I'll take the Heathrow Express over the alternatives because it is a much more compelling option to get to downtown London. Recently in Johannesburg the airport rail took me to the airport in 14 minutes where as a car would take 90 minutes in commuter traffic. In Germany, I've seen people commute half way across the country every day on high-speed rail because it opened up opportunities to work that didn't exist before.