the reason they don't twirl up into a ball is because after constantly being handled they eventually realize that being in a ball isn't going to stop a human from touching them so they eventually realize you aren't a threat and give up on balling. A BP in the wild though doesn't have interaction daily with humans so they will have a greater instinct to ball up. There is a smaller chance they would attack or bite because their instinct will just tell them to hide in the wild, so, although there is always a risk to pick up a wild ball, it isn't as great as other snakes could be.