I have never kept count, but a lot of people who come to see me after they are injured in an auto wreck chose not go to the emergency room. Sometimes the adrenaline is running, and they do not think they are hurt. Other times, they are concerned about the cost of medical care. Either way, it's a good idea to get checked out if you have been in any kind of significant wreck.
Recently, a Cave Junction man died three days after he was in a one car wreck. After losing control, the driver flipped his truck. The driver refused medical treatment at the scene, but three days later, died in the hospital.
Would immediate care have saved his life. I don't know. However, I have had clients of my own refuse care, only later to end up at the hospital in serious condition. It makes sense to be safe, and get checked out.