How to analyze the deep intention of distinguishing Cantonese from Mandarin in Guangdong Love Story?

Many songs are a mixture of Mandarin and Cantonese, such as "Break Up" by Wang Leehom Lu Qiaoyin and "It won't rain" by Huang Kaiqin Liang Yanling. It's just a musical expression. Why dig deep into what is the meaning? It's like the Chinese text teacher analyzed more than a dozen meanings that the author didn't even think of.