Contracting isn't always that cut and dry. Different industries and sectors of employment can use it for indefinite employment, and as such, many people can end up relying and hoping for longest possible work. I.e., USA Federal Contracting. Creating a union to protect workers and fight for financial fairness isn't something that Contractors should be excluded from -- it is still work after all. And in the case above-mentioned the actual workers do not negotiate with the contract issuer, but the middleman, a contract company -- human capital.