Why Raeder's surface fleet mattered even when its ships rarely fought

Why did Erich Raeder support a surface fleet when Germany could instead concentrate on submarines?

The surface fleet forced costly British dispersion across multiple theaters and missions that a single-purpose submarine threat would not reproduce.

Raeder's support for a surface fleet is explained through the extra threat it imposed on Britain. British capital ships needed destroyer escorts, and holding a force against German surface ships kept those vessels from other duties. A German fleet concentrated on submarines would make it easier for Britain to mass-produce small anti-submarine auxiliaries across the Empire. Capital ships and carriers could then be concentrated against Italy and Japan. The counterfactual includes stronger Mediterranean carrier operations and an Indian Ocean reserve to sustain them.