To make a few extra bucks, they have made the seats narrower through the years — all to get an extra seat per row. This has resulted in narrower seats, and a narrower walkway. This is part of the reason it is so easy to get hit by the drink cart going down the aisle and why you feel like a sardine, even with "normal" sized people around you. It is also why tall people feel so squished, as they have stolen leg room to fit more rows.

Sure, it makes it so they can get more seats on the plane, which lowers prices slightly. At the same time, it's made flying uncomfortable; too many people in too small a space, particularly confined, as you are, for a few hours.