It makes him feel in his game. This was taken before the scramble section. Usually he doesn't hike with it on, but in this case perhaps it was also for warmth. In winter I have used my helmet as a hat before.
"As an adolescent I aspired to lasting fame, I craved factual certainty, and I thirsted for a meaningful vision of human life - so I became a scientist. This is like becoming an archbishop so you can meet girls."