In NJ it is the law. The courts have made a public policy finding that making sure all emplyees are covered trumps other considerations. This drives up the cost of an employer carrying comp insurance, which is mandatory of all employers. One can make the argument that hiring illegals at lower pay offsets the higher cost of the insurance premium. And yes, some schools in NJ are highly burdened by illegal aliens. And yes, realtors are showing listings by the room. Seeing it first hand.
I knew about the hospitals, and the schools, too. The realtor info astounds me! Are these rooms in private homes, zoned one family? Are they apartments or condos? I heard a term awhile back that I wasn't familiar with -"stacking'. It was an article about too many people in some communities living in two-families, one-family homes, etc. Owners were renting out attics, basements, etc. putting up sheetrock to divide rooms. Sounds like it's one in the same thing.