Why do dialects sometimes have comedic effects?

Dialects are often purer spoken languages ??that can more naturally abandon the rigidity of written language. Make the characters and language more vivid, more humane, more down-to-earth, and easier to be convinced and accepted. Some dialects have been given some "natural" character. These stereotypes are available. For example, Shandong is bold and rude, Jiangsu, Zhejiang and Shanghai are calculating, and Tianjin is "叏儿". Dialects are often the languages ??spoken by ordinary people and the people at the bottom. Many sentences and lines, spoken in such language, have a deconstructive meaning in themselves.