1. Economists say that free trade mathematically helps everyone -- makes everyone richer.
2. But if hurts certain sub-populations within countries who work in certain industries. Center-left economists will then say that the "losers" of globalization or free trade should be compensated, helped or supported in some way.
3. But this hardly ever actually happens. Even though it doesn't happen, economists continue to call for free trade.
4. The losers of free trade revolt at the ballot box.
Why does it work this way? "Free trade" agreements are not simply agreements that countries will hold down tariffs. They are bundled in with all sorts of items that favor global elites and the global financial system: intellectual property, restrictions on regulation, restrictions on support of national industries. They are a vehicle for the managerial/professional class, negotiated in secret and without public input. These elites never will spend money on compensating the losers of free trade. For them to do so, these agreements would have to arise from popular politics, the product of organizations that would demand that vulnerable segments of the public not lose out. That is not the class background or ideology that produces free trade agreements, and that is not the power that backs them.
Mainstream economists have a dual function (or perhaps a singular function) as the ideologues of the global managerial class. That is why they will never cease supporting free trade even as the compensation of losers that they say should happen never does.