The same issue is prevalent here in Michigan. The summer season is obviously the worst, and the fall is surprisingly busy too. This isn't an issue everywhere of course with some parts much harder to get into than others. Getting a site in Ludington State Park for example is similar to getting tickets to a popular concert. Once the 6 month window opens, just start clicking and take what you get, if you get something. It took a friend of ours two years to get in.
As also posted in this thread, I too think it may be a mid term issue. RV'ing is very popular currently, more so than it has been in many years. If there is indeed an economic "slow-down" around the corner, many people will reconsider this lifestyle and its requisite expenditures.