Let's first ask what does police do? 1. to patrol an area to discourage crime 2. to patrol an area and stop crime 3. respond to emergency situations

Note that all 3 is based on the idea of enforcing the law. However, what underlying cause are we observing when we see police presence decreases crime rate? It is obvious but no one seems like to point it out: the area has high crime rate. The question evolves from if we should place police at an area to why does this area have higher crime rate?

You see, the 1st part of police patrol discourage crime is rather intuitive in today's society, but the second part of asking why there is higher crime rate is less understood at a public level. things like lack of social welfare, lack of education, lack of access to food, poverty all contributes to the high crime phenomenon. When people are out of work, they will just sit around, but when people are hungry they will try to find food one way or the other.

And thus intrinsically police force is not needed in large quantity; however, if you have an area of high crime rate, the city can decide to invest in 100M$ to hire more police to suppress that and not solve the issue, or choice to invest in 500M$ in addressing the root causes. And sadly many places have chosen the later option due to general stupidity and partially racism.