Sleeping Under the Stars?

I stopped at a Welcome Center just inside the Indiana state line returning from Illinois on I-74. It was time for my ten hour break. When I woke up in the morning I saw a couple that had laid a mattress down on the parking lot and was sleeping there. I would be afraid that someone would run over me if I did that. Before I had left the rest area attendants told them they had to sleep in their car, not on the parking lot.