Care about what they say.

Hello, great people there. I would like to ask a question about usage of "about" that has bothered me for a long time. Here are two sentences. Could you tell me if there is some nuance to tell.

I do not care what they say VS. I do not care about what they say.

Although I feel like there is not much difference, there must be a reason to use "about" there, so I would like to hear your thoughts about it.

Thank you in advance and have a good day.