Utility trailers, altough not classified as a vehicle, are usually required to have their own title and license plate.
Another favorable argument to an utility trailer is when the load can damage the pickup bed. It's particularly more critical in a modern coupé-utility, such as the Chevrolet Tornado/Montana/Opel Corsa Utility, which unibody layout makes harder to replace the body panels without compromising the structural integrity.
It's also important to consider the extra loads over the pulling vehicle's stock brakes, engine and driveline. Common-sense is recommended to ensure the trailer wouldn't compromise too much the overall safety and the durability of the vehicle, which could turn the budget aspect less favorable.