Hi! I've recently come across the phrase "for all (someone) cares" and GPT told me it's a fixed English idiom. Is that right?

I know it's not meant literally. I've often heard it in TV shows and movies, but I never thought about it grammatically. I find its capability of producing an ironic meaning is interesting!

For example:
He can quit tomorrow, for all I care.
→ I really don't care if he quits tomorrow.

Question

Hi! I've recently come across the phrase "for all (someone) cares" and GPT told me it's a fixed English idiom. Is that right?

I know it's not meant literally. I've often heard it in TV shows and movies, but I never thought about it grammatically. I find its capability of producing an ironic meaning is interesting!

For example:
He can quit tomorrow, for all I care.
→ I really don't care if he quits tomorrow.

Answer

Hi Shana, 
It is an intriguing phrase. Sometimes a dismissive tone like "for all I care" can actually sound better than a simple negation or protest.

If the lottery winner isn’t serving the greater good, for all I care, let them pave their driveway with gold blocks.