Policies that are economically optimal, like "free trade", are often promoted as beneficial to the whole public. However, these policies have winners and losers. Theoretically, the losers could be compensated by redistributing some of the gains of the winners. Then no one would be worse off, and the economy as a whole would be better off.
However, winners have every incentive to fight this redistribution and are more often than not successful because they are more powerful than losers, practically by definition. This means that the best course of action from the would-be losers' self-interested point of view is to try to prevent the policy from being instituted at all.