airline seating distinctions, whatever they are called, actually break down into Misery, Misery Lite, and the highest achievable grade, Slightly Comfortable.
Although one of the commenters has come up with a story with that perfect blend of "possibly apocraphyl, but just might be true":
Basically, to fly a person across the Atlantic costed just a little more than an economy class ticket. All the profit is made in business class and, especially, in first class. In fact, business and first slightly subsidise the economy class. So why carry economy passengers at all? Well, this was told to me by a senior BA executive, without economy class passengers the aircraft would be too light and the turbulence would bounce the first class passengers about too much. Yes - economy passenger are ballast to keep first class passengers comfortable.