Given the prices I see for eating out in Europe (I remember a chain pizza place in London was like 20 pounds for a single pizza), it's probably more out of necessity, we also have lost most of the cultural trappings of a slow meal.

In America there are tons of places offering instant meals for a dollar. Fine cuisine and the time honored art of dining (as they experience in France on every meal) is lost. Food is fuel, and you can get a salty, satisfying meal for only a few bucks here which leaves more time to go watch TV, play WoW etc...