Perhaps they shouldn't even show Staten Island. What is the point of including Staten Island on maps displayed on the Manhattan, Long Island and mainland parts

Perhaps they shouldn't even show Staten Island. What is the point of including Staten Island on maps displayed on the Manhattan, Long Island and mainland parts of New York, given that you can never catch a train there? Conversely, what is the point of displaying maps showing the rest of New York on Staten Island? Especially given that there is only one public transport connection between the two!