The performance of a voice anonymization system is typically measured according to its ability to hide the speaker's identity and keep the data's utility for downstream tasks. This means that the requirements the anonymization should fulfill depend on the context in which it is used and may differ greatly between use cases. However, these use cases are rarely specified in research papers. In this paper, we study the implications of use case-specific requirements on the design of voice anonymization methods. We perform an extensive literature analysis and user study to collect possible use cases and to understand the expectations of the general public towards such tools. Based on these studies, we propose the first taxonomy of use cases for voice anonymization, and derive a set of requirements and design criteria for method development and evaluation. Using this scheme, we propose to focus more on use case-oriented research and development of voice anonymization systems.