The people making the laws are the same ones pushing the H!B agenda...the laws in this country increasingly do not favor it's constituents, rather it's capitalists and those who can afford to 'buy' the laws to ensure their profits.
A single worker usually doesn't have the political and legal acumen to be able to represent themselves in negotiations. Like it or not, there is strength in numbers. A company can callously fire or mistreat an employee w/out the support of his fellow workers, it's considerably harder to do so when there is an organization that watches out for his rights. I will agree that there is corruption and graft in the unions, but that is true of ANY organization once it becomes large and established. A board of directors have their own (and supposedly their stockholders)) best interests at heart and will do anything to maximize that profit margin. Having a counterbalance like a union to look out for the welfare of the workers, and in a lot of cases the company itself is a good thing.