Acetaminophen recall -- Metal fragments found in generic caplets

Earlier today 11 million bottles of generic acetaminophen were voluntarily recalled due to metal fragments found in 500 mg caplets. Acetaminophen is most commonly known as the active ingredient in Tylenol, but this recall only affects some generic "store brand" labels and not the popular brand name. The metal fragments, some as large as one third of an inch (that's huge!), were discovered during quality checks done by Perrigo Co. and contaminate as many as 383 batches of the medication. Perrigo Co. is the largest supplier of store brand acetaminophen, and sites both raw materials purchased from a third-party supplier and run-down equipment as possible causes.

According to the FDA the metal bits don't pose any serious health threats, with most likely ill-effects being a stomach ache or small cuts to the mouth or throat. Up to 129 stores may be affected, including some big names like Wal-Mart, Safeway, and SuperValu Inc. If you're concerned there is a list of all stores possibly affected as well as the FDA's official list of recalled batch numbers.

Okay, it can happen. But my question: Why was the quality control check being done after the medication was sold and distributed to stores?