Unions are the only way a large group of workers can get any parity with a small number of owners.
If we truly had more morality based owners/corporations, we wouldn't need unions, but we don't. The guiding principle to too many today is greed and greed alone.
The pity is that the "greedy" corporate leaders know nothing about so much that they mistake paying low wages with increasing profits.
Henry Ford opposed Unions because he saw them as a tool of the Mob. He also paid his workers significantly better than other companies, because he saw well recompensed workers as a benefit to a company. The result was one of the most successful corporations in the 20th century.
Like the free market, Unions are not panacea for all worker ills. Many unions no longer have any interest except siphoning money from both workers and bosses. A change is needed in the way Unions operate.