Normally, unions exist to work for the interests of labor, to work for a living wage and fair compensation, and to try and ensure that workers partake in profits that they, in no small part, generate.
Hence it is deeply ironic that the one industry where workers - and these folks have indeed regular contracts with a set wage plus a bonus structure - really do partake in profit-sharing to a very large degree is the same industry that unions love to hate. In other words, where workers have realized the unions' goal of being able to siphon off large portions of profits for the workers, the ones whose labor made those profits first possible, it is organized labor that is one of the most vociferous critics of exactly that which the unions would love to have for their membership.
The Financial Intermediation industry, of course. Bankers, traders, brokers, all have their very large incomes not through their wages, but through the bonuses they earn by earning their companies very large amounts.
Got to love the irony in that.