Human beings' decisions are sometimes made by the work of hormones, Including marriage. Why do people......?

This is the problem with a materialistically inclined mundane world, which thinks and tries to explain everything in available, mundane scientific manner, which is indeed inadequate. When you try to explain mothers love in terms of neurons and hormones, mothers love ceases to be mothers love at all. This is a category mistake, and read Gilbert Ryle and his book 'Concept of Mind; to know more about category mistake.