There are many reasons actually, but here's the one I currently consider most important: National Parks never close. Take Palo Dura State Park outside of Amarillo, Texas. Were it a National Park, I would be there right now. But it's not, it's a state park and so I'm sitting in a hotel room in Amarillo.
Of course everyone knows that nature shuts down at 10 PM, so it's not totally surprising that state parks close then. It's not just a Texas problem either, most Georgia parks close at the same time.
Palo Dura likes to call itself "The Grand Canyon of Texas." It may well be, but I'll never know. And neither will the five or so other cars that turned around and headed back to Amarillo because the park gates were shut.
The funny thing is, the highway is littered with billboards promoting the park. For 200 miles I was enticed to detour over to the park and not once did any of them mention that it closed at 10. Here's what Palo Dura canyon looks like, should you after 10PM:
So I drove on to Amarillo, got a cheap motel room and crashed out for the night.
Now it's on to a national park that I know will be open no matter what time I arrive: Great Sand Dune National Park.