Starships are at their most vulnerable when they are unoccupied and docked. At this point, it is entirely defenseless. Every starship has a crew, and just as the crew had needs, so does the ship they occupy. When docking on a planet, Starports will provide the shelter that these starships need during this time. Because of this undeniable need, many businessmen will charge a premium for the level of protection that these Starports provide.
The concept of charging for this service is a point of contrition amongst many members of modern society. Even so, the practice is conducted despite the ethical gray area, if only because it is a proven consistency that people who are desperate will pay almost any price.