I'd agree only if our benchmark of comparison is "I want to travel while sleeping", but the value of flying is that you get there so fast that you usually don't even need to sleep. The journey from Chicago to SF is eight times longer by train than by plane, and, price aside, the only value proposition is a (very) scenic view; considering price, you can either spend half the price of flying in exchange for two rough nights stretched diagonally across two train seats, or five times the price of flying for two nights of decent sleep.