It is incorrect to feel that incisional hernias never open. The overall risk of incisional hernia is 11% and that number can vary based on the specifics of the operation and the patient.
The inguinal area is more prone to herniation because of the collagen in the area being abnormal. Also, we are upright beings, so there is more pressure in the pelvis. Lastly, male pelvis is narrow, so from a physics standpoint there are more forces into the inguinal canal than in females.