I believe none of them require proof of employment eligibility e.g. immigration papers so it's a way for those on the fringes of society to make a living. It's

I believe none of them require proof of employment eligibility e.g. immigration papers so it's a way for those on the fringes of society to make a living. It's basically the same as why people work bad jobs for cash that is less than minimum wage. There are several layers of illegality here but nobody dares speak up.