The bonuses you speak of are limited to a very small percentage of the at-will group.
Not true. The few at the top receiving the large amounts is all that many ever see or understand. Those get the print or make the best press headlines. I don't agree with the extremes of many bonuses at the top. But a few thousand employees are at will. You will never infuse a company with good college grads, if year after year you will never see a bonus or raise, even for exemplary work, just because the union groups didn't also get one.