If you can’t avoid making the mistake again in the future, your boss wants to know that, and saying sorry doesn’t help with that.
I understand this is a common way to talk about professional relationships, but this just isn’t even remotely true. Saying sorry doesn’t help anywhere as much as Just Not Being A Fuckup, but it is often the only thing I have agency over in a situation and to say knowing how to say sorry right in a situation has played a critical role in my life unfortunately.