Despite being incredibly wealthy, why was the Parsi merchant Ratanji so unhappy?

Ratanji, a famous and religious Parsi merchant from the Nizam's state, was immensely wealthy with vast properties and a charitable nature. However, as described in Chapter 14, he was consumed by an inner worry that made his life feel incomplete. The source of his deep sadness was that he did not have a son. While he had twelve daughters, the absence of a male heir to carry on his lineage caused him constant distress. This made him feel that his worldly happiness and immense wealth were ultimately fruitless, causing him to be perpetually uneasy and sad.