Drifted Cowboy, We do. We make the choices what is right and wrong. Some choices are highly controversial. If we don't like it, we can do something about it. Petitioning comes to mind.
But we can't always make pure democratic decisions because getting the entire united states together to decide on every topic that needs addressed is physically impossible. There isn't enough time to do that, either. So we elect representatives to make decisions for us. Many decisions are made with our Republic. We are not a true democracy, but more of a republic.
Or we can move if we don't like where we are living. Living in the United States is cool in a way because different states experiment with different rules and social norms. When one state has an idea that works, other states can adopt those ideas. If a state doesn't change, then we can move to a state that better agrees with our philosophies and lifestyles. I don't live in California because it is to socialistic for me. I live in Montana because that state has lost fewer freedoms than most other states.
Almost everything is grey and not black and white. I wouldn't call most things arbitrary; there are reasons, science, experience, etc. that goes into making a decision that affects society. Are arbitrary decisions made and implemented? Yes, but they are not common.
Let's take pooping on the sidewalk. That is far from arbitrary. There are health considerations. It is visually unpleasant as well as smelly. It makes walking on the sidewalk more hazardous because the poo would trip us up. Most of society agrees with that, so we have made a decision to not poop on the sidewalk. Some people still do, though. Some don't care. Some do it just "because" (arbitrarily). Some do it to be mean.
We will always have conflict. We won't always agree. Some rules change over time as society changes. But we make the choices. Even if we choose not to make a choice, we are still making a choice and that affects the society we take part in. Unless you are a hermit living in a cave in a remote corner of the world, you will need to make choices to live with your neighbor.
In regards to living in a vehicle, that is far outside the norm. When one lives so frugally and so freely, that is a problem. A lot of people are forced into that situation because of there poor choices, and those poor choices follow them and manifest in garbage being strewn about. Loud music/noise disrupting neighbors. These are problems with a relatively high number of homeless/poor people. What is the answer? I don't know enough to give a detailed, highly specific answer, but I do know that we will be a part of that decision making process. Part of that process is forums like these.
I didn't understand your last sentence.