Engineering Management - Process
A process created and implemented by the individual contributors themselves is much more tuned to optimize the real work being done. A process designed by managers at best approximates the actual flow of work that it needs to govern, optimize, or codify. This is the source of many clueless and inefficient processes.
People feel greater ownership over process they create themselves, and are thus more empowered to adjust it in the future as circumstances inevitably evolve rather than allow it to calcify. Process imposed externally ("from above") is more difficult to break down and tends to be unnecessarily enshrined, thus producing extra organizational inertia.