Then again this is the result of culture shock between Europe and the USA. I've sat in cars, and at steps, and at sidewalks, at those hours and later and absolutely nothing has happened or ever will.
In fact, let me provide an example where I'm actually bitten in the ass by this. In my neighbourhood (incidentally considered the very "worst" one in Madrid) it becomes common in summer for groups of people to get drunk and talk extremely loud on the street right in front of my house, up to and beyond 3-4 AM, even on weekdays, which is as you might understand less than desirable when you yourself have to get up early for work the next day. You can call the cops for them drinking on the street (which is technically illegal at any hour), and they'll at tell them to stop doing that. If they're not drinking, and you're lucky, the cops might tell them to quiet down. They absolutely cannot tell anyone to leave the street no matter the hour and no matter what part of the city, and if one of them tried, it would be seen as a ridiculously fascistic abuse of authority. This is in fact the story of how I learned to depend on earplugs.
In other words, what is common sense or not depends entirely on the country you live in. You may convince me that cops in your country and area can make people vacate the street, and if they were disturbing sleep at high hours I would be all for that, but if someone isn't doing anything of the sort, you won't convince me forcing them to leave is common sense on the grounds of it being "suspicious", nor do I want to live in a country like that.
