Workman bikes are often bought by employers to be ridden by their employees, who can't be presumed to know or care anything about riding and/or maintaining bikes.
I suspect that one of the benefits of over-building them is that making them so heavy greatly reduces the temptation for the employees to joyride and/or see how fast they can ride them on or off the warehouse/factory floor. Somehow, I don't see Boeing wanting its workers deadheading back to the parts area at 20+ mph inside the factory.