carriers wont defend themselves

i am at periscope depth not on surface, periscope is up and i have just torpedo a ship next to the carrier. the DD start scouting for me and are on alert since being triggered to do so by my attack.

the carrier has no trigger to respond to a sub attack other than changing direction.

it launches a few planes at surface ships but if only my sub is around i can sink the whole convoy and never see a plane try to find and attack me.

planes that are already in the air will attack me and if the carrier has launched planes at some other target they will respond to attack me sometimes but never if i am only threat around.

i see the carriers change coarse and such responding to my presence but why doesnt it use its best weapon, the planes, to defend itself and the convoy it guards?