The article isn't about taking the train instead of the car, but about taking the train instead of the airplane. Taking the airplane is way cheaper and more convenient than taking the train at the distances the article is talking about.
Some people manage to read or watch movies at least on the flight itself but personally my head hits the pillow before the plane even leaves the runway. I’m not sure what soporific magic is at play here. Anyway, I avoid flying as much as possible as a consequence.
Do you mean "London City". Unless you're an incredibly rich footballer Stansted is far from convenient to anything.
As for convenience, if you fly budget, there's always baggage restrictions and you always have to waste 2 plus hours at the airport.