Spanking is done by lazy parents who wish to convey the message that violence is the way to control other people.
Why do you think is lazy? parents spank because they think it is the only way, at least in my case. I don't hold a grudge towards my parents because they both come from uneducated backgrounds, my late grandparents would beat the crap out of my parents and it just continued.
We have been now enlightened and know it is not the correct way of parenting. But some people like Shirley still think that spanking is okay if you don't leave marks.