Yes - you do really need the law and the police to stop people being killed and robbed. Couple of years ago in London there was a riot and the Police let it be known that they would only be protecting life - not property. Within 6 hours, people were being burnt out of their homes, there was widespread looting and people were beaten to death in the streets within 48 hours.
That's the law of nature. Our legal systems are a collective effort to have something better.
If you had a company in the marketplace providing protection, and they said they weren't going to fulfil their contractual obligations to protect property, do you know what would happen? They would lose customers and go out of business. Pity that the Police have no such obligations toward us and can pick and choose what and who they want to protect, isn't it? It isn't for nothing that people say you have to be either rich or important to get justice in our society. They are the only people the Police really care about because they are the ones who can kick up a stink through using either their money or friends in high places. The rest of us? we pay whether we like it or not. Whether we get good service or not.
So when you see police out in force to protect the politicians, it's not such a surprise when you realise that they are the police's true customers. The ones who pay their salaries. They mostly don't care about the rest of us.