What's the point of this joke?

There is a Adu Chu Shi in Sichuan who likes painting and calligraphy. He has hundreds of treasures. Among them, there is a bullfighting picture painted by Dai Song, which he cherishes very much. He used brocade as a painting bag and jade as a painting axis, and always carried it with him.

One day, he spread out his calligraphy and painting to dry. A shepherd boy saw this painting, clapped his hands and said with a smile, "This painting is a bullfight. When a cow fights, its strength is used in the corner and its tail is drawn between its legs. Now the cows in this painting are wagging their tails and fighting, which is wrong. " Du smiled and thought he was right.

There is an old saying: "Ask the farmer for farming and the maid for weaving." This truth will not change!