Point being: most people will go through their entire lives doing nothing that would draw the attention of the cops: with or without the police. But that's not all the people, it's just most of the people. The police aren't there because of most people, so saying how most people are, therefore we don't need police at all, is just wrong. It's like saying we don't need sheep dogs because there are 100 sheep and only one wolf. We have police because those most people who wouldn't hurt a fly are easy pickings for those few people who would screw everyone else over given a chance. There's a reason 23% of people in prison check out as diagnosable psychopaths, and that's not because society is unfairly biased against psychopaths.
Also note how people are constantly pressuring the police for results / convictions of people they don't like, and these demands come constantly from both the left and right of politics:think about the justified stuff about how they're not catching and convicting enough rapists: guilty until proven innocent in those cases. Being pressured to ramp up the conviction rate, no matter the crime, is going to lead to many more miscarriages of justice. The police do hate crimes, so get rid of the police. Then, when someone else does a hate crime, we're incensed that those people are getting away with it, and not stopped and arrested.
So we want a perfectly non-harmful police who also proactively come down like a ton of bricks on whichever bad guys we say should be locked up and throw away the key. It's not easy, this is an extremely hard needle to thread. Benefit of the doubt and you let someone go with a warning, next thing you find out that you're the cop who let Jeffrey Dahmer go or something. Obviously some nations have massive room for improvement, but it's never going be balanced well enough to probably please anyone, since most people actually think law enforcement is being both too lenient and too strict at the same time, but for different things.