Why the US Navy retained triple-expansion engines

Why did the US Navy retain vertical triple-expansion engines for so long?

Long-range Pacific requirements, reliability, turbine cost, and congressional constraints made proven triple-expansion machinery an attractive compromise.

The discussion links the US Navy's long-range requirement to its Pacific geography and Philippine commitments. It also contrasts the reliability and lower cost of mature triple-expansion machinery with early turbine expense and supplier problems, including congressional pressure over the cost of turbines. The result is a reminder that propulsion choices emerge from strategic reach and procurement politics, not engineering preference alone.