I've seen them in posher suburban towns and a lot of HOAs. It's usually worded that no more than 2-4 non relatives can share a single residence. You won't find it in the more working class towns and cities. I have seen some Florida coastal towns, like the Keys, enable a maximum in order to push out the working poor who may be living 6-8 in a 2-bedroom house or apartment.

You aren't in the neighborhoods where this has been in place. But it doesn't mean its not happening.

It happens informally everywhere. People will let friends or family move in and split the rent. In many places the landlord is never around and nobody is watching the property so they get away with it.