Since all the weight is in the front, why not make them front wheel drive for better traction. I'm betting anyone that has a 2 wheel drive pickup and has slipped on ice or just gravel has asked that question.
transmission for front wheel drives are not durable and are not designed to handle the potential stress of a 1000+ pound load that a pickup truck could amass. Also, front wheel drive transmissions do NOT like to tow anything.
A rear drive transmission gives the strength and stability if you have a heavy load.
FWD's also chew up tires faster, and don't produce the torque needed to pull a tree stump out for instance. Handling wise.. it's really up to the tires.