I was checking out a really nice woman at Old Navy today. When the transaction was almost over, her phone started ringing.
She checked the phone and didn't answer it. It rang a second time.
She looked at it again, presumably deciding whether or not to answer. It rang a third time.
She said, "Oh, I know this is rude, I'm so sorry," and ANSWERED THE PHONE.
Here's how life works. If you know something is rude, you don't do it. The fact that you're apologizing does not make it any better. At all.
The same rule applies when you're the last person leaving the store. Saying you're sorry does NOT excuse it.