People who are larger (either taller or fatter) require more room, and tend to weigh more (in both cases) -> so if they accidentally bump into the plugged headphone jack they are more likely to cause damage.

It sounds plausible on paper, but this is just Reddit-level-research, so maybe it's completely unrelated! maybe you're just unlucky on flights.

Man, charging a fee to use shitty airplane headphones is entrapment...