Final answer:
Plural marriages are entered into for a variety of reasons, including economic, political, or religious factors. Economic benefits in agrarian societies, political alliances, and religious practices are all common motivators for plural marriages. Changes in societal norms and increased opportunities for women can also influence marriage structures.
Step-by-step explanation:
The question is asking for reasons why people might enter into plural marriages. Plural marriages can occur for a variety of reasons, including economic necessity, diplomatic alliances, or religious convictions. For instance, in agricultural societies, polygyny (a man having multiple wives) may be practiced to increase the labor force for farming activities. Economic reasons such as resource management within a family unit can be a significant motivator. Additionally, plural marriages might be used as a tool for political alliances, strengthening ties between families or groups. Lastly, certain religious beliefs may endorse or advocate for plural marriages as part of their traditions.
In contrast, societal trends such as improvements in female education and economic opportunities, advances in gender equality, and access to family planning can lead to reductions in fertility rates, influencing marriage customs and structures. Societal norms and legal frameworks in many countries encourage monogamous marriages, while others accept or even promote plural marriages for various reasons.