Why does the history of discarded scientific theories support instrumentalist arguments?

The history of discarded scientific theories supports instrumentalist arguments through a line of reasoning often called the "pessimistic induction on the history of science".1

Instrumentalists argue that because the history of science is filled with theories that were once considered highly successful but were later proven false—such as the ether theory of light—there is no logical basis to assume that our current, successful theories are any closer to the truth.21

This perspective challenges the realist assumption that the predictive success of a theory serves as evidence for its truth. If past scientists were equally convinced of their theories' accuracy based on similar empirical successes, yet were ultimately wrong, instrumentalists contend that we have no reason to believe contemporary theories are different. Consequently, they argue that scientific theories should be viewed primarily as tools for solving problems and generating accurate predictions, rather than as literal descriptions of an external reality. By focusing on utility rather than truth, instrumentalism avoids the risk of committing to the existence of unobservable entities that may later be discarded.21