Piloted aircraft must carry at least one human, as well as the fuel required to carry the human and weapons to the desired ranges. The human is needed to operate and guide the weapon systems during the second stage of weapon delivery namely, the delivery by aircraft. Because most of today's weapons are rather "dumb" (with some weapons dumber than others), the human provides a means to reprogram them during delivery from the ship to the target.
The aircraft takes a tactically significant amount of time to move the weapon to the target. During that time, tactical conditions may change, necessitating rapid human intervention in weapon delivery. Thus the human in the decision loop: the aircrew selects from a set of targets and assigns weapons, while continuously evaluating the tactical environment based on information obtained through onboard sensors and via radio nets that relay information obtained through onboard sensors and via radio nets that relay information from other databases (a cruiser's or a carrier's, for example) and making necessary adjustments. By bringing human observation and analysis (and instinct) in communication with the weapons, the pilot adds flexibility and agility to the second stage of weapon delivery.
Navy aircraft are large also because they must carry many weapons. To conserve warfighting time by making fewer transits, many weapons are carried per sortie. Moreover, targets and combat conditions may change in transit, so sometimes it is necessary to carry different weapons on the same sortie.
Obviously, a human is needed to return the aircraft (which is a recoverable second stage of the weapon system) to the ship (the first stage of the weapon system). The physical laws of impulse and momentum dictate the use of large, extremely strong aircraft. There is no getting around the fact that combat aircraft must be able to endure repeated launches and recoveries and survive combat damage.