Why do states have a minimum on hours worked law to be eligible for health insurance? The law protects who?

Some states like NJ & NY set a minimum number of hours that must be worked in order for the employee to be considered eligible for the employee health insurance. Why is there this law? Who does it protect, the employer, the employee, or the health insurance company? If it is to protect the employer, why not rely on employer policy. Likewise, if it is to protect the insurance company, why can't the insurance company rely on a contractual minimum hours policy? It seems strange that state law would require such a condition.
--------------------
If you are not a full time employee he is not required to provide group health insurance for you and that saves him money. You may want to work full time but he has the right according to law not to pay for your health insurance if you work fewer hours. That is all over the U.S. It is optional for employer to offer health insurance because it has become so expensive.
Source