Why anti-submarine ships need manoeuvrability

Why do anti-submarine ships need manoeuvrability if they are not especially fast?

They must position hull sonars and handle towed arrays effectively, which often requires turning the entire ship.

Directional hull sonar may be aimed most effectively by turning the vessel that carries it. Moving the whole ship can produce a better search geometry than trying to steer the sensor alone. A towed array adds limits on how rapidly and tightly the ship should manoeuvre. Good handling therefore lets the crew reposition its sensors without fouling or degrading them.