Hiring a JNI (Java Native Interface) developer can be a strategic move for projects that need to bridge Java with applications written in other languages like C, C++, or assembly. JNI developers can effectively integrate and leverage native code, providing performance improvements, access to hardware-specific features, or use of legacy code. Their expertise ensures seamless interoperability, efficient memory management, and enhanced application performance. Thus, their skills can be crucial for complex, high-performance, and hardware-dependent applications.