Staten Island is in a pretty central location. You can go straight to brooklyn / queens / long island without having to go through the city like you would from NJ.
With that said, I haven’t looked at the toll situation for either of the NJ bridges in years, so maybe tolls alone would be enough to remove any alleged savings from non-union labor.
That area also has some of the longest commutes and traffic in the country. In my mind, it doesn't make much sense for time sensitive deliveries or efficiency.