I never could understand why anyone would make a hitch out of material that is heavier than the frame it is connected to??:? Looks like a weight loss program is in order!%)
Maybe because to make it out of lighter material would just be plain stupid perhaps?
And to waste your time trying to find a trailer hitch, or components, made from material just exactly the same thickness as your frame would be a stupid waste of time perhaps?
And since, even though often using a thinner material, most frames are of much greater cross-section, multi-layered, bent and channeled (and, in the case of a Bronco, fully boxed), so have a much higher specific strength than just the material thickness alone would indicate, under-engineering any tow device simply to save weight on a truck that nobody really knows how much might be tow with it someday, would be stupid?
So to
not make it stronger than the surrounding material, when you have to build around existing obstacles like a gas tank, where you want to keep flexing to a minimum and impact resistance to a maximum, would be just as stupid. Especially if it's your business.
And since most anybody making hitches for a living (which just might be who made his hitch after all) is going to have much of their on-hand material of the strongest stuff they would normally have reason to use, so that they can get the best price on bulk material. And so they won't be under-building a product for the guy with a 1953 ex-military Power Wagon that needs a hitch, yet don't really see using the same material for a vehicle (like a Bronco) with less towing need as "over-building", and don't want any complaints or lawsuits when something does happen because, instead of the hitch failing when the guy overloaded it, the truck's frame failed. So it's not his problem any more.
And even when done by an individual, a lot of times that's the only material they have laying around the ranch or garage at the time. So they used it. Or it's what they could source at the time. So they used it.
Or, maybe they need a bigger surface (in the case of a bumper) to fill a specific purpose that we don't know about.
Or, maybe they just like the look.
What's to understand?
Paul