为什么使用熔融数据帧而不是使用强制数据帧（反之亦然）

We were going over dataframes in my statistics class today, and my instructor told us about a 'molten' type and a 'cast' type. I understand what the differences are and how to convert between the two - but why would I do this? What, if anything, makes one of them more/less useful than the other? Are there specific cases where one would be preferable to the other?We were going over dataframes in my statistics