Must be specific locations. We've not had any problems getting into anywhere, with a little planning and some reservations. Another tip, we don't camp at the high profile parks. We enjoy the unknowns, out of the way, places that don't draw a lot of go-getters. Camping is peaceful, and depending on week-end or week-day, or holiday or not, may be filled up or may not.
I suppose, being older, we ran and did so much when the kids were little, we enjoy the quiet, peaceful, low activity, places. Indiana has several State Parks, some not so popular as others, but as far as camping goes, you couldn't ask for anything nicer. The problem is if you want to park somewhere with a high profile energy atmosphere. Yea, those are crowded and can be unruly.
We've noticed an increase of seasonal campers in private parks though.