The law is not intended to be the final say on socially positive behavior, it just defines behavior so bad the the state has been given the power to punish it.

Think of the law as only a foundation upon which to build the real society we ultimately want, where people are good to each other above and beyond the bare minimum required.

A given act can seem arbitrarily labeled as good etiquette if violations of it don't bother you. But surely you'd agree that there are some norms our society is widely agreed to be better off for practicing, despite no legal requirement for doing so. It's not necessarily going to be all the same norms you'd care about. We're all different people and won't agree about all of them. But we can make life easier for each other and ourselves by making an effort to adhere to them where possible and practical.

I'm not advocating against social norms. But just those that don't make sense and only exist because they already exist.

My personal design for 'the society we ultimately want' would be social norms based in proper values (i.e. being nice to eachother, allowing people the freedom to do whatever, not being bothersome, etc.). From that would follow the norm to give up your seat to an old person, and the norm to help your elderly neighbor carry something heavy.

From that would not follow that we can't wear our hats indoors, or that we need to say sir and madam, or that we're not allowed to play music on speakers in public, or that we can't have a call on speaker phone.

If someone is being obnoxiously loud is a different matter.