Final answer:
Remote PICs must request ATC authorization early in controlled airspaces to ensure safety, prevent collisions, and to be integrated into the traffic flow efficiently by ATC, promoting a smooth operation for all airspace users.
Step-by-step explanation:
The reason why Remote Pilot in Command (PIC) should request ATC authorization as soon as possible before operating in Class B, C, D airspace and within the lateral boundaries of the surface area of Class E airspace designated for an airport is primarily for safety and air traffic management. Controlled airspaces (Class B, C, D, and surface area of Class E) are regions of the sky that require additional rules and communication due to high traffic volumes and the potential for mixed types of operations, including both manned and unmanned aircraft. Coordination with ATC ensures that remote PICs are integrated into the airspace system without risking collisions or interfering with other traffic. This also allows ATC to manage the traffic flow efficiently, and notifying ATC promptly can result in quicker authorizations and less disruption to the operation of the aircraft.