It's simply what middle America expects, which is what the driver is for virtually all American airlines. Things develop differently in different regions - the US has "First" Class for the front end of flights within the region, comprising wider seats, more legroom but disgusting food (if any at all) and bad service, with no lounge access. Europe has "Business" Class for the front end, with the same seats, but blocked middle, lounge access and better food and service. And that's exactly what the bulk of customers expect.