Pickup truck advertising is certainly about masculinity. You've already mentioned the hard work and heavy haulin', Andrew. What about that deep, deep voice intoning that the big powerful truck will make others see you "like a boss, like a pro." Doesn't that make your testosterone surge? 
The funny thing is, most of those trucks are never used for anything heavy or dirty. Many are bought with a semi-permanent cover over the bed, which will still be virgin-pure at trade-in time. So, the pickup truck serves many as a modern codpiece. It's a pity though, all the extra space they take up and the extra emissions.