Because it was designed as a convoy/fleet air defence/network
ship. Or at least that is what the RSN say. That it was to be the
nexus of a networked fleet, hence it needs a bit of fleet defence
capability.
And though the missile/JSOW has a very long range, it still has
to get to range = 0 to kill a target. This is where your chance to
save yourself or your ship consort comes in. Though if weasel is
right, you probably only have a shot at the bomb/missile, not the
actual fighter as it is very far out of range that even if you shot
at it, it has a lot of time to evade.
I still don't want ANY pilot or fighter in SAM range though, a
single lucky shot and a 100M dollar plane can go splash for the
cost of a "xxx K" SAM. Not to mention the loss of combat efficiency
with the loss of a plane from a squadron. weasel probably has the
best idea, flood the ships AA with so many targets from range that
one is bound to hit.
"Throw in very combustible rocket fuel that keeps burning, the
ship will die either from a thousand cuts, or just burn to death.
Mind, these missiles travel at MACH 4 and above. Kinetic energy
alone would pierce most ship's hulls."
Remember the Shefield!!! :)
This is also why CIWS is getting out of date, a wall of 20mm
can't stop a Mach 2-4 missile even if it hits, the momentum is too
great, the debris and the solid fuel booster will still coast into
the target on momentum alone. This is one of the reason for larger
calibre air-defence guns nowadays. At least with a larger calibre,
the chance of knocking the trash to one side is greater.