I shuffled toward 17F, put my bag in the overhead, and then all-too-abruptly sat down. After nearly breaking my tailbone on the faux-cushioned seat, I realized I had made a poor decision. Baffled why an airline would make its passengers endure this discomfort, I did some research and learned that airlines are installing thinner seats to reduce aircraft weight. Makes sense — lighter planes fly more efficiently. So less weight requires less fuel, or less power.