Exactly. Well that and the details aren't spelled out by the airlines either . When you pick economy the seats may or may not be as advertised. The same airline and the same plane can have different configurations. Dimensions of space aren't listed anywhere when booking a seat.
Airlines are running into physical space issues. In their quest for ever more seats The airlines are beginning to ignore basic human needs. People need to move around. The tighter and more closed off you make people feel the more likely they are to get into arguments. This is not only true physically, but mentally as well. Arguments lead to fighting.
It is why Cities have always struggled. To many people to close to each other. The wealthy always purchase enough space to make themselves comfortable. However the poor can not and once you get so many people pressed together they fight. That fighting spills outward and you have a riot over a simple issue that is dealt normally dealt fairly.