Ski areas have always done a big share (25% or more) of their total business during the holidays. As others have pointed out families do not have other options since many schools frown on taking the kids out for a vacation. Our kids were all good students and we were able to do it in the 70s and early 80s and skied when it was not as crowded or expensive. The kids took their homework and made up any tests when they got back. The schools our 8 grandkids attend are not that liberal about taking time off today.
The ski industry does have lots of future problems....climate change, high cost, declining numbers of skiers/riders, fewer local areas to bring people into the sport, and way too much work. I am not sure if we would have done so much skiing with our kids if the costs were as high as they are today and we could only travel on the busy holiday times.