I Don't Know But… - A way of saying, ‘I don’t give a damn,’ usually when you’re

A way of saying, ‘I don’t give a damn,’ usually when you’re too lazy to talk to someone.

He said, ‘I don’t know,’ and then went back to gaming.

She said, ‘I don’t know,’ and walked out of the conversation.

My friend said, ‘I don’t know,’ and then started eating pizza.