I think it's illegal to spank so that parents will think long and hard about doing so rather than just thinking it's ok and normal to use such measures.

I have a 2 and a half year old daughter and she causes no end of temptation at times, but even though I live in a country where there is no laws against spanking I still wouldn't do it as I don't want her to speak that sort of 'body language' or have any concept that it even exists.