Originally Posted by shefgab

In Europe, the majority of people sitting in Business class pay for it (for whatever reason, mostly on business accounts I guess), whereas in the States it's mostly frequent flyers. As such the airlines wanted to be able to maximise the extra income fro selling a J ticket, so "flexi seating" was introduced. It makes sense on to have a flexible seating concept where you might sell 50 J seats in the morning to Frankfurt, but then the same plane will do a lunchtime trip to Bilbao, with just 8 J seats sold, but plenty of Y seats.
Also bear in mind, the average sector length in the USA is much longer than that in Europe. I think the majority of European flights are less than 3 hours. Despite the differences in comfort, people in Europe are still paying for "an upgrade economy seat", and Americans still generally aren't paying for the domestic "first" seat.