Why is penetration testing important in order to keep systems secure$?$

Penetration tests allow security professionals to objectively determine the security level of a system so that any weaknesses can be addressed

Successful penetration of a system's defenses mean that it has been deemed secure

It isn't $-$ Hackers perform penetration testing and will use the results to attack the systems in the future

It isn't $-$ Security professionals aren't as skilled as hackers and might accidentally harm the systems