In theory, yes, you could enforce better conduct (although this might harm the bottom line). But I also think that when you place people in cramped conditions,

In theory, yes, you could enforce better conduct (although this might harm the bottom line). But I also think that when you place people in cramped conditions, they inherently begin to behave more antisocially and become less amicable. For every inch of legroom or width you shave off a seat, I think there's a non-negligible amount of discomfort that leads to more annoyance, which in turn leads to worse behavior. At some point, some portion of the consumers do explode into outright hostility or madness, and the airlines mostly seem to be tuning their services to just above that point. Money - the very high cost of any air travel prior to deregulation - used to somewhat alleviate both issues. The airlines had incentive to compete on service quality rather than chase the maximum number of seats they could pack on a plane. And anyone paying that much to fly had a reputational incentive to behave in a civilized way. Flying private for the same amount of inflation-adjusted money as first class cost in the 1960s is a poor analogue, because it inherently leaves out the social dynamic that caused people to, e.g., wear their best clothes and don their best manners to board an airplane. There is no analogue, because first class now is not much better than what coach was back then. In other words, public air travel as it is now is a product that did not exist in the 1960s, geared to a consumer who didn't exist. And the enshittification is inevitable when the goal is maximum occupancy. If there were an airline with double the legroom in coach for double the price of coach on other airlines, I'd fly it exclusively. No one offers that. It's a barbell with steerage at one end and a very diminished first class experience for 5x the price at the other.