I'd extend this from "kids" to "dependents". Anyone trying to move a disabled person, or simply an elderly relative, will opt for private transportation. For me it is a question of reliability. If the train is cancelled, the bus is late, or the power goes out, the private car allows a degree of privacy and safety unmatched by public transport. You think changing a kids diaper on the train is bad, try it with a 150lb wheelchair-bound adult, one who may not have the mental capacity to understand why the train has stopped.