Government does not promise to magically take care of everything. And even if they did, the citizens run the government. Any shortfalls in government are ultimately the responsibility of the citizens.
It's not a legal requirement. It's a moral requirement. It's your country, your state, your city. It's your government. You are legally allowed to shirk some of your duties, although not all of them, but that doesn't make you less of a shirker..
Parenting is similar: there are a lot of ways to be a shitty parent that don't rise to the legal level of neglect.
"Of, by, and for the people" is not subjective. Neither is the people replacing the sovereign. Nor the nature of a community as a collaborative enterprise.