Final answer:
The nuclear family has become rarer than before due to changes in societal norms, increases in diverse family structures, and changes in reproductive technologies.
Step-by-step explanation:
The term 'nuclear family' refers to a family structure that consists of one or two parents and their immediate offspring. However, this traditional model has become rarer in recent years for several reasons. Firstly, changes in societal norms have led to a greater acceptance and recognition of diverse family structures, such as cohabiting parents, single parents, same-sex parents, and extended households. Secondly, factors like increases in divorce rates and the rise of single-parent households have contributed to the decline of the nuclear family. Lastly, changes in reproductive technologies and adoption have made it possible for individuals and couples to have children outside of traditional marriage.