Both try to get more for doing nothing in return. Both are motivated by greed. It's almost like the people who run corporations and the people who work in them are both just people looking out for #1.
Companies will strategize to try and make more profit for doing little or nothing in return...just like Unions will strategize to get more money while offering nothing in return. It is just life and the human condition.
I really respect people (both corporations and workers/unions) when they approach income/profit from the angle of what can we offer or do that would create more value to then make more money in return - rather than just try to force their way into a higher paycheck.
Two sides of the same coin. People tend to pick one side or the other, but really they often act the same - which really is nothing less than I'd expect.