One summer while in college, I spent time working in the QA/prototype lab for a local specialty transformer/power supply company. One thing we did was test transformers as pulled from several points along the production line. Waiting until a transformer was completely built and ready to go out the door was no time to find it didn’t meet spec—especially if it were mil-spec.
Likewise, why would you wait until a food batch is finished to check it for quality—only to find that a key ingredient was causing an off-flavor or other inconsistency in the final product? Off-spec ingredients, metal or plastic fragments in the product or an ineffective kill-step process could literally kill your business if bad product gets out the door. Quality checks can’t wait until the final inspection point; they need to be done with incoming ingredients through each step of the process and right down to packaging and shipping.