You’re right about the size of the seats, but it isn’t always that people are fatter in this country. People might not be fat, but maybe they have broad shoulders or just a wider body in general — such as a football player. I don’t know about elsewhere, but most of our local buses are built in Japan where people tend to be more compact.
As to the purchases of buses, I would think that is something that an individual could bring up before the city spenders galore, and point out the mishandling of funds.