I'm not going to defend stereotyping. There are lots of legitimate uses for a pickup truck, whether it be hauling things around or off-road capabilities.

In the suburban environment where I live, the majority of pickup trucks are effectively commuter cars. They haul their owners' asses to a cubicle farm and back home again. These are people who fully buy into the stereotype and have bought a truck so they can purchase their masculinity on a monthly payment plan.