They never wore hard helmets Few pilots in any air force in WW2 wore helmets. Flying Helmet to keep head warm, to fix oxygen mask to and to hold headphones perhaps but not for protection. However, would it be unreasonable to try and keep alive until the target of a suicide mission is reached? I bet that modern suicide bombers look both ways when they cross the road.
I think that the hard helmet worn by pilots in these latter days is to protect them when they go through the canopy during ejection.