The Brothel Law

Here's a picture of a church because for some reason
when I think of brothels I think of church.

I've known about the Brothel Law for a while now, but it's one of those things you don't really know you know until you realize you know. If that makes sense. But anyway, I know about it and I've been thinking about it lately.
It kinda varies from state to state. Like in Illinois it's six unrelated women. In one state it was four unrelated women. In Missouri, it's four unrelated people, period. Since I live in Missouri, that's the state I'm going to focus on.
Now four unrelated people. That's not very hard to do. A lot of time a few girls or guys will all get their first apartment together so that they can afford their rent and all of their other things they need for basic living. So let's say in the scenario there are two girls, and those two girls have their boyfriends are living with them. The two girls aren't related, and they're not legally related to their boyfriends either. So right there they are all sitting ducks waiting to see if the police are gonna arrest them or not.
In all reality, this law isn't really enforced, and let's face it, most people don't even know it exists so it's not really a big deal. But it's just one of those things if a cop really wanted to, could arrest you for this, or at the very least fine you.
That's kind of a scary thing to think about. How many laws do you think are out there that you don't know about? How many things are there that people do regularly that's actually illegal? How many things do you think you do that if a cop really wanted to, could arrest you for but they don't just from a lack of the law being popular or enforced. What's the point of even having these laws if no one's going to enforce them?