Why do cruise ships need pilot boats?

Some older large vessels need to be pushed into position by pilot boats in tight spaces because they only have one set of screws (propellers) at the aft (rear) for forward propulsion. Modern day cruise ships have several sets of omni-directional screws for greater maneuverability, but still need pilot boats for emergency directional changes as well as communication to aid in navigation in tight spaces.

Yes, azipods and bow-thrusters do help for maneuverability, but it's a tugboat's job to help steer the vessel. The pilot boat's job is to tell the captain how to navigate in waters that he and the helmsman are unfamiliar with. So, cruise ships still need pilot boats (and always will) but most don't need tugboats.