A Mach Kernel developer is crucial for developing and maintaining low-level operating systems, especially those based on the Mach Kernel like iOS and MacOS. They possess deep knowledge of system level programming, inter-process communication, memory management, and hardware interfaces. Their expertise can lead to better system performance, stability, and security. They can also help in developing proprietary systems or modifying existing ones to meet unique business needs, giving your company a competitive edge. Their skills can prove invaluable in creating efficient, robust, and secure systems.