I always wear my SPH5. Have been flying for about seven years and haven't flown without it for about six and a half of those seven years. I fly an R22.
I have asked other pilots who do commercial ops with tourist type flying or flying schools, why they don't wear a helmet and they all have said words to the effect, "I know I should but...." and add to it "passengers get a bit nervous when they see me in helmet and they've got a set of headphones."
Doesn't stop me though. I use mine all the time. It's my brain that'll get rattled around in a crash.