What does a child learn from being hit by a parent? Is it really necessary? - the child learns not to misbehave. But I agree with you - reasoning, grounding or stopping pocket money are much better ways to get children to behave.
I'm also glad that corporal punishment was done away with in secondary schools.
It is the lazy option - in many cases, I'm sure it is.
I think there may be differences in cultural attitudes to smacking children - again, the African women beating seven shades out of her daughter above doesn't compare to the occasional smack I received as a child.