Hiring a HyperCard developer could be beneficial if you're dealing with legacy systems or educational tools, as HyperCard was popular in education and multimedia applications. These developers have a unique skill set, understanding the foundational concepts of GUI-based applications and user-friendly software design. They could provide insights into simplicity and user-centered design, and apply their problem-solving skills to more modern languages and systems. Additionally, their knowledge in scripting language could be beneficial in automating tasks. However, HyperCard is an obsolete technology, so it's important to consider the specific needs of your project.