why no close range missile defence for fighters?

These days, helicopters have lasers that can damage the IR heads on SAMs; ships have long had radar guided guns and missiles to take out low flying anti-ship missiles, and are actively working on even faster lasers; and now, ground vehicles have access to an active denial system that can intercept RPGs seconds after launch, at minimum ranges.

Yet the best defence fighters have against AAMs and SAMs these days are flares, ECM, decoys and manouvering, mostly defensive measures. Why is there no system to actively destroy these missiles, especially since there is often some time between launch and impact, giving time to respond? Plus the IR signature or active radar guidance heads on these missiles are often easy to track, and thus target, especially because missiles tend to fly by very predictable routes. Also, missiles being relatively fragile machines, they need not be destroyed completely, just damaging them slightly or physically obstructing them is likely to take them out of action.

The 70 mm missiles could be used. With a basic IR or radio guided guidance system, these would come relatively cheap. Plus, they’re currently being developed into guided missiles for precision ground attack use, meaing you just need to change the guidance system.

The Hydra 70 for example costs $1,000 for the basic missile, add another $4,000 for the guidance system? It has a range of up to 10 km, and a speed of about Mach 3.5.
Against say an AMRAAM ($700,000) with a speed of Mach 4, a first Hydra could be launched to intercept at maximum range, and than the fighter aircraft would have another 8 seconds to launch more Hydra’s if the first one failed to stop the enemy missile.
On top of this, the Hydra’s could also be used offensively in dog fights, launching a large number of missiles. In a world where fighters are few between and carry a limited number of missiles, this would give the Hydra user a clear advantage in combat endurance.

Another alternative I can think off are basic explosive, launched in great numbers behind or below the aircraft, designed to wander into the enemy missile’s flight path and stopping it through sheer explosive and kinetic force, like flying mines.