The answer is a simple one. Since people come in all shapes and sizes, why are airline seats all the same (think sardines). I am 5'9" and weigh about 180 and it is a snug fit for me. It is not just obese people either. What about people who are very tall? How does someone 6'5" squeeze into those tiny seats? Where do their legs go? This is a case of maximizing profit at the expense of the people who create the profit.