Some of the more adaptable passengers can achieve comfort in coach on LD trains while others like ourselves lean towards the sleepers. David looks really comfortable on that trip.
We find coach to be perfectly fine on trips up to 8 hours in length; plenty of legroom and a comfortable seat. For overnight trips though, the comfort of a bedroom is appealing to us. My wife has trouble sleeping on the train as it is, and won't do coach overnight. However, we know a few folks that have gone coast to coast in coach and they loved it. LD in coach is just a matter of taste and how well one can adjust. Most LD passengers do ride in coach.