This has always been one of life's great imponderables. Another question George Carlin used in his comedy routine.
Okay, for anyone who may not know World War II history, kamikaze pilots were Japanese suicide pilots who deliberately flew their planes into Allied warships. These attacks took place during the closing stages of the Pacific campaign of the war. Kamikaze planes were often filled with bombs and explosives, so as to do more damage to the U.S. naval vessels.
Now, let's get back to our original question: If these guys were suicide pilots, flying to their own intended destruction, why the heck did they wear helmets?
First of all, kamikaze pilots never did wear helmets. This is a misnomer. They wore soft leather flying caps, the kind we see Charles Lindbergh and Amelia Earhart wear in old films.
These flying caps covered their head and ears. They kept the pilots from getting too cold or even going deaf while flying with their cockpit canopy open. (A canopy is a transparent hood over the plane's cockpit).
Unlike most regular pilots, who would close the canopy while flying, kamikazes needed their canopies open to get a better view when taking off, landing, or looking for landmarks.
And even if kamikazes had access to modern aviation helmets, it would almost surely be a pointless exercise for him to wear them. Anyone who knows anything about aviation, or even gravity, knows that if an airplane crashes into a solid object like a warship, a pilot's helmet isn't going to do the person much good. A plane crashing (usually at full speed) into a warship, normally results in death for the pilot, no matter what he wears on his head- whether a helmet or a leather flying cap.
What a flying cap is good for, however, is protecting the pilot's head from getting knocked by the plane's canopy during high-speed mid-air maneuvering. Like the kind you have to do to avoid gunfire while nosediving into a ship.
Couple this with another little-known factor about kamikaze pilots: their missions were often aborted. Kamikaze missions were often scrapped before the final planned explosive attack because of turbulence, bad weather, or visibility issues. The pilot's protective headgear could, in these cases, ironically, protect the future suicide bombers. And the kamikaze who survived today, lived to complete his suicide mission another day.