Shaming... it's been a thing for a long, long time. Why?

When a person has already completed something, what is the point in shaming them about it? Is it to make them a mockery so others within society don't do the same thing those who shame/mock about? How is shaming/mocking the person helpful to the person? What is done is done. Apparently, shaming/mocking people helps societies become stronger? How?

I find this "shaming" concept interesting within societies but also find it horrendous based on mental health aspects. Some seem to think they are doing their society a 'favor' but what I see is people contributing to more harm. What do you think?

Here's just one of many examples: