Rocket-delivered anti-submarine torpedoes

Why are torpedoes not carried close to a target by a missile before entering the water?

ASROC, SUBROC, and Russian systems already apply versions of the idea, but limited investment kept it from becoming a dominant weapon category.

The proposed hybrid is not hypothetical. ASROC and SUBROC carry an anti-submarine payload rapidly toward a contact before water entry or detonation. Russian systems provide further variations. The concept's limited visibility reflects the level and direction of investment in anti-ship and anti-submarine weapons rather than physical impossibility.