An apology that admits the wrong lets the victim stop doubting or blaming themselves. So the anger comes after it is acknowledged that what was done to you is wrong. In that way, anger after an apology actually means it may have worked.
If that's true (you will get punished for apologising), then there is no incentive for the guilty party to ever apologise.
Who would want more punishment on top of what they already had?
An apology that admits the wrong lets the victim stop doubting or blaming themselves. So the anger comes after it is acknowledged that what was done to you is wrong. In that way, anger after an apology actually means it may have worked.