Well, funny you ask.
This started back in the 6.0 engines. Every diesel engine built by IH/Navistar (6.9/7.3 IDI, 7.3/6.0/6.4 PSD) had a block heater installed. Even all the way back to the 6.9 IDI in 1983, when Ford put the engine in the truck, they installed and routed the cord to the front into the area behind the bumper. This was standard practice on all diesel engine installs, E and F series into the 6.0 equipped vehicles. The early 6.0's (like my 03 Excursion) also had the block heater cord. Sometime during the 6.0 run, maybe the 05 grille/headlight change, Ford changed the policy. If the vehicle was not sold into a "cold" environment (not sure what the Ford official definition of cold is) then it would not receive a block heater cord. However, if you wanted a block heater cord and weren't in a "cold" environment, you could buy one from the parts department, as and accessory for $90. Or goto an IH/Navistar dealer and buy one from them for $25-30.......