It's a good question. The very purpose of a union is to protect its members even at a cost to everyone else. The chicago plumbers union for instance fought succ

It's a good question. The very purpose of a union is to protect its members even at a cost to everyone else. The chicago plumbers union for instance fought successfully over and over to prevent the city from switching their aging lead water piping infrastructure to a composite type. The reason? Lead water piping required more billable hours of maintenance. The result was that Chicagoans had to pay more money to continue drinking from a poisoned water supply, and the plumbers got richer at their expense. In general, there is little evidence that cartels produce net benefits, whether they deal in oil or in labour or in anything else. I suppose the average person is sympathetic to unions both because they can see themselves as a plumber more easily than as an oil sheikh, and because the societal costs of labour unions are hidden and do not take shape in a very tangible form, be they high import tariffs, reduced R&D spending, bad water infrastructure, or more expensive and noncompetitive goods and services, among other things. Regardless, the economics of cartels will never be sound.