I'm not sure that is entirely correct. It is the material of choice for some people. I was on a tour 2 years ago where it rained 35 out of 90 days, and I was glad that I had a synthetic bag. I have both synthetic and down bags, but prefer the synthetic for everything except prolonged temps well below freezing.

Even for most mountaineering and winter camping here in the Pacific Northwest, I still prefer my synthetic bag.

Synthetic bags are easier to wash and they dry quicker than down bags. While setting up camp in a campground, a dog walked over to my bag that was laying on the ground and pee'd on it. A quick trip to the laundry facility in the campground fixed the problem.