Fire hydrants mark the exclusive parking spaces of employees of New York City.
If you are not an employee of New York City, do you know what happens to you if you park in front of one? You get a stiff traffic citation reminding you to never do that again.
If you are an employee of the city, or the state, you are exempt from such citations. You can block as many fire hydrants as you want, because the fire hydrants belong to you. They were put there so public employees will have a place to park when they come home from work.