If the convention is changed, that's fine.

Simply ignoring the convention, as some do, seems ruthless.

There is no way to change it other than to ignore it. Are you imagining some cultural council you can appeal to to change it? The culture is nothing but thousands of individual decisions.

> There is no way to change it other than to ignore it.

Couldn't one change the culture without freeloading off of where it's baked in?

For example, publicize your preferred convention, and then give your business to restaurants that decide to satisfy the demand for that convention.

If people don't flock to those restaurants, then maybe that wasn't a viable cultural change.

Or maybe the objection wasn't impassioned philosophical position on the optimal economic model, but rather that they simply wanted to pay less, and blaming a questionable custom was a convenient loophole.