Building software agents that make decisions based on human values presents a complex challenge. This is a first attempt to systematically review trends in how researchers represent, select, evaluate, and implement values in software agents. The review highlights two key limitations in the field. First, most research adopts or acknowledges Schwartz's theory of basic human values, but often simplifies its complexity. Second, many studies oversimplify the notion of values in general, failing to utilize established theories from psychology or philosophy. Additionally, the review finds that common software tools and existing frameworks, like the Belief-Desire-Intention model, are frequently used without fully considering their underlying principles. This research offers valuable contributions to the field of value-based decision-making in software agents, exposing research gaps and limitations in current research, and highlighting the need for a more nuanced approach. By calling for researchers to integrate insights from economics, social science, psychology, and neuroscience, the review paves the way for the development of more sophisticated agents that can navigate the complexities of real-world decision-making.