The author also mentions "Although it may seem like the company is saving money — because you don’t have to provide temporary workers with medical coverage or paid vacation time."
I just want to point out that contractors actually cost the company MORE money than employees, on average around $30k/year per worker. I think the main reason contractors are used is because many full-time employees "settle" somewhat and don't have the same drive that contractors do (i.e., contractors feel they have more to prove and are thus more productive). Also, contractors can be fired without any consequences, which is not to be said about employees. But I don't think cost is the main driver here.