Question: As most crashes are on takeoff and landing, and fire is the real killer, most often. Why not have breakaway wings? That's where the gas is. Let's assume a plane has to make a hard landing..upon touchdown/contact jettison the wings. They serve no purpose at that point and they definitely kill people. Breakaway parts/modules are employed in many arenas, so why not wings?

Answer: 
Just wanted to add that if wings were to be 'disengaged' when needed/emergency-case, the aeroplane-fuselage or a 'metal Tube' now will fall faster than a human would free fall, there will be nothing to slow it down (assuming pilot/autoPilot can still control wing-control-surfaces or whatever its called).   

If the aeroplane is very close to ground or on ground and moving, discarding the wings now means throwing them away with undercarriage, the wings would most likely tumble and continue to move with the plane and may be even into it.   

But if the aeroplane is on ground and not moving and then the wings are disconnected, means the Plane still has wings next to it, but now the fuselage is below it. The fuselage could roll and make it difficult to evacuate.
Also, lot of aviation fuel (30% or more) is in Central tank + ACT. i.e. in fuselage.
The early 310s with "tuna tanks" were designed with exactly this scenario in mind. The idea was that the tanks would keep the fuel as far from the cabin as possible and [shear off](https://www.aopa.org/go-fly/aircraft-and-ownership/aircraft-fact-sheets/cessna-310) in a crash. Cessna abandoned this idea some years later when they incorporated aux tanks into the wings (310L) and then later into the nacelles (310N).

I do not know if data exists to quantify the effectiveness of this design feature.