There is a big difference with semantics here....
The hitch (the physical piece) just bolts on and is just moments to add to any vehicle. This is great if all you want to do is toss on a bike rack or cargo carrier.
The wiring is where the hiccup lies. If you did not order the option from the factory, you are missing the trailer control module. This is what the 7 pin trailer plug connects to on the vehicle side. In addition to providing the correct outputs for the 7 pin trailer connector, it interfaces with the rest of the vehicle and adjusts the other vehicle parameters when a trailer is detected (such as turning off rear parking sensors, altering the stability control profile, etc). There is nothing preventing you from purchasing the factory 7 pin connector and wiring to the trailer module (TRM), and there is nothing preventing you from purchasing the TRM itself. However, when the TRM is connected to the vehicle (the wiring connector that interfaces the rest of the connections to the TRM should exist), the rest of the vehicle will start to throw errors, because those other modules in your vehicle are not coded to have the TRM as part of their system. In theory this could be alleviated, however, the coding is not dealer controlled, but automatically created based upon the initial build/VIN of the vehicle, thus the dealer could not click a few boxes to get the other modules to correctly recognize the TRM on the vehicle's communication bus