The weather is warm. They do not have to wear heavy clothes to keep warm.
VOA: special.2009.06.22
Others wear heavy metal equipment for protection.
VOA: special.2009.06.16
Last year, federal regulators blamed heavy tube wear in the generators on a botched computer analysis that they said badly misjudged how water and steam would flow in the reactors, along with manufacturing problems.
While it looks like it'd be heavy and hefty to wear, the device is very comfortable to wear for short periods of time and the ear cups are extra soft to avoid that pinned-back feeling you get with heavier hardware.