Earlier quoted context omitted.
Mainly because they were introduced when the seats were set farther apart. Now companies squeeze more rows and keep the same seats. But also because with any shared resource there's an expectation of decency involved. Some people just betray that expectation. They're the ones with the mentality that "they shouldn't have served alcohol if they didn't want me to get insufferably drunk", "they shouldn't have put the can…
People generally didn’t even offer her a seat on the metro. And letting other people decide whether you should be permitted to use the functionality the airline has given you is dysfunctional people pleasing.
Your "dysfunctional people pleasing" is someone else's "not being a total dick". As I said, there's no law against it. It's all about character and education (or lack thereof). Some people even think they must brag about it because why else would they have a mouth and keyboard.