Why does the company accept health certificates? Can't employees keep it for themselves?

Article 9 of Chapter II of the Labor Contract Law stipulates that "the employer shall not detain the employee's resident identity card and other documents, and shall not require the employee to provide a guarantee or charge the employee fees in other names." I won't elaborate on other documents here. Under normal circumstances, similar food enterprises need employees to have health certificates. Most of the health certificates here are collected by the company for the convenience of all departments when they check in. The collection of documents has written evidence or process instructions, even if you resign and leave. The company will not give it to you. Health certificate, not gold bars. I thought the same thing.