One of the primary reasons corporations are concerned with turnover is because of the tremendous level of consistency that can be achieved when there is always someone around who was "here when it happened" QC/QA is the glue that ensures that all parties and all levels of the product cycle are in sync.

This can be tremendously helpful in preventing meetings for the purpose of remembering what we decided at some meeting in the past, and arguing about who understood what. With QC/QA ensuring that all steps of the process are completed and vetted, no one can justifiably argue that they thought something else would happen. Fewer trips to the top of the cycle are needed and people not directly involved in a particular phase of the operation can then be tasked to other aspects of running the company without countless and repetitive interruptions.

By getting QC/QA involved earlier in the process, bugs can be found much earlier, allowing for less re-coding and re-design. The more you eliminate however the faster your product gets out the door. This process is also rumored to cut down on a lot of tension related illness, however this is just a rumor and is left to the reader to decide if it's true.