Why do commercial helo pilots wear helmets? I've been on my fair share of commercial helo rides, primarily in Canada.  Over the course of more than ten rides in three different kind of helos (Bell 407, 412, and I think one other) there was only one time when the pilot wasn't wearing a helmet.

It's worth noting that these flights were taking off and landing in very remote areas of the Selkirk mountains, usually on glaciers. 

At the same time, I have been around (US) flight schools since I was 15 years old, and I've never seen an instructor or student helo pilot (flying R22s and similar) wear a helmet.  Also, fixed wing pilots don't wear helmets.

Why do commercial helicopter pilots wear helmets, when instructors and students don't?

It's a little hard to see, but here's a photo of one of the choppers, and you can see that the pilot is wearing a helmet.
The same reason as anyone would wear a helmet - to protect their cranium in circumstances when there is the possibility of damage to that area of the body.

Helicopter operations are often low level, sometimes over dangerous terrain and, unlike fixed wing aircraft, they do not have the option to glide away from an engine failure. Low-level operations may not afford the pilot the altitude required for a successful autorotation landing so there is the possibility that they will be going down hard and fast. 

Taking an example of low-level flight over forestry resulting in a forced landing, this may be survivable, but the pilot will be thrown around quite a bit as the aircraft is buffeted by the trees as it goes down. Some head protection would be important to the survivability of this crash.

There are a few other reasons I could think of apart from the main one above


Some helicopters operate with doors open, up where the birds fly around. A seagul to the head would not make for a happy flight
Noise - helo's can be louder than Fixed wing and the helmets could provide better noise cancelling
Specialist helo operations such as S&amp;R use equipment such as night vision, which could be mounted on a helmet
Habit - ex-military helicopter pilots could just be in the habit of wearing a helmet, and carry this over to civilian operations.