For safety reasons.
It was an attempt at keeping some humans employed. More staff at the place also reduced crime.
$$$$$ rules in other places.
I don't know. In Oregon there is no self-service. Takes getting used to, but the pumpers are surprisingly quick. This was done for the jobs mainly. And I suppose it does provide some sort of basis for a safety net.
There have been some odd laws trying to preserve jobs that are outmoded. At one time, teens worked at gas stations pumping gas. When self-service stations came into being, some people thought they were eliminating jobs, so they passed laws. But now teens in most states work in air-conditioned malls in the food court.
The reason why self-service gas stations are forbidden in New Jersey because I think the governor of New Jersey has seen a customer at a self-service gas station turning the gas nozzle like a key and that is not a proper way to insert the gas nozzle and turning the gas nozzle like a key can break the gas nozzle which destruction of a property which is not good so that's why self-service gas stations are forbidden in New Jersey.