Why do dry batteries leak oil？

Acid zinc manganese battery, with a shell made of zinc, and its internal electrochemical reaction is:

The negative electrode reaction is:

Please note that the raw material for this reaction includes zinc (Zn), which is continuously consumed as a negative electrode material during the discharge process of acidic zinc manganese batteries. In other words, as the discharge progresses, the zinc shell of the battery will continue to thin. In the end, a weak part of the zinc shell will be depleted, causing perforation, and other substances inside will flow out of this hole. This reaction basically only occurs during the discharge process, and if the discharge circuit is disconnected, no current will occur. So, batteries with continuous discharge are more prone to leakage, and batteries that are not in use are less prone to leakage when removed