Why a submarine would fire an IDAS missile

Why do modern German diesel-electric submarines carry the submarine-launched IDAS air-defense system?

To disrupt an aircraft or helicopter that has already found them, creating a brief escape window rather than trying to fight for air superiority.

Concealment remains the submarine's preferred defence against hunting aircraft because firing a weapon confirms its presence. A submarine-launched missile becomes more attractive once a helicopter or patrol aircraft has already found the boat and is approaching to attack. The aircraft must then react to the threat instead of continuing its attack undisturbed. Evasive manoeuvres and defensive measures give the submarine time to move away, even if no aircraft is destroyed. The argument is strongest in confined waters such as the Baltic, where simply escaping unnoticed is more difficult.