Even though the barrier to entry is high, and isn't in the same ball-park as these car-campers there are far too many people trying to spend some time under the trees, and the park is being damaged.
Contrast this period with the 1980's. Disposable income is (apparently) lower now then it was back then. Back in my childhood several of my neighbours would have campers, or boats, or snowmobiles; and many opportunities to use them throughout the year. Now when I look around I only see 1 on my entire block, and with entire segments of the economy closing for good, factories being emptied; I see the golden era of the union, and 'extra' money as a thing of the past.
So how are all these people able to afford crowding our parks? The article talks about this decline almost as if it's a recent thing, but I have seen this same pattern going back over 10 years.
The only way I can find a reasonable amount of peace and quiet is to goto Crown Land, and multi-day canoe trips into the wild.