3. Cops use performative enforcement in poor neighborhoods because it yields metrics important to them with minimal effort.
Poor neighborhoods are often demanding and crying out for enforcement of laws. Nobody wants to live next to a crackhouse, and the people forced to lack options to leave. In my city, there's a notorious drug house that has been in operation since I was in college in the 1990s. It has better staying power than Walmart -- it's still there. What poor people in general resent to the point of riot about is systematic bullshit and abuse on the part of ineffective police.
When the powers that be say "clean up that area", they round up stupid kids for bullshit, maybe hit up a few street dealers, etc. The actual hard work, say arresting street gang leadership or investigating property crimes isn't sexy and takes time. The best documented examples are NYPD, where the worship of Excel sheets resulted in sweeps where the cops would issue appearance tickets for such offenses as "obstructing the public sidewalk" (ironically doing so, btw, when they are literally parking their personal vehicles on sidewalks for these big sweeps), than run through and make arrests for failure to appear a few months later.
Shotspotter in particular is stupid - it's just a way to blow Federal grant money. If as you say, the police "know where the crime is", why would they need microphones to tell them where gunshots go off? Presumable they patrol high risk areas and hear it themselves.
Police departments are paramilitary organizations. That means they need a military like level of accountability and discipline to function well, and the nature of modern governance is such that that is lacking. The Army doesn't tolerate drunken soliders runing amok, but police departments do. IMO the best way to address the issues of policing is to consolidate smaller departments into state or regional entities to both professionalize and reduce the chummy nature of what goes on.
