It was often made in the past when people did not have a lot of money or access to ingredients. The ingredients are few and common, so it did not cost much money to make. Plus for the many people that lived on farms, they could produce all of the ingredients themselves. The meal is quite filling, so when eaten at lunch, it can sustain (fill) a person for the rest of the day's work. The recipe got handed down through generations, so people still make and enjoy it today. It can be found in almost every restaurant and most people know how to make it from memory themselves.
