That same line of reasoning could apply to music on planes. No one really needs to use a particular airline at a particular time or use a public park at any given time. It ceases to be a public place if a small group of people can de facto monopolize it by making it unpleasant for most other people to be there.
James Q. Wilson talked about this problem a long time ago... and why standard neighborhood shaming cannot really police it. Maybe there is an increasingly different set of norms among different generations which is why you have a breakdown in manners and even high school kids from affluent areas hitting "devious licks."
Because the sanctions employed are subtle, informal, and delicate, not everyone is equally vulnerable to everyone else’s discipline. Furthermore, if there is not a generally shared agreement as to appropriate standards of conduct, these sanctions will be inadequate to correct such deviations as occur. A slight departure from a norm is set right by a casual remark; a commitment to a different norm is very hard to alter, unless, of course, the deviant party is “eager to fit in,” in which case he is not committed to the different norm at all but simply looking for signs as to what the preferred norms may be.