I agree with Shawn, you have to accept the fact that it's all instrument flying at night offshore, from hover to skids down. It can be done, and is being done, but it's not nearly as safe as daylight flying. I've had SICs try to fly into the water on downwind to an isolated rig, and I've had them unable to complete an approach to landing, even after several tries. The approach and landing are as demanding as anything I've ever done. I enjoyed the challenge when I was doing it, but I was very careful during every flight, right up to engine shutdown. As to why, there is one reason, and it's the standard one. Money. Money drives everything.