That implies that they do care, to some extent. Surely you couldn’t care less?
This has been discussed before here, and it is an American usage that, like you, I didn’t understand at all, having grown up with “I couldn’t care less”, which makes more sense on the surface.
But I understand it now. It’s quite dry. It means “I suppose I could care even less than I currently do, but that would require extra effort that’s not worth making.” It’s subtle. I like it.
Uh… in the US that’s considered non-standard too, you know. Only idiots say “could care less” rather than “couldn’t.” I can understand your confusion though, if you’ve mostly read it on message boards. Lots of idiots in the US enjoy posting on message boards.
And writing successful rock songs…
- Green Day, Jesus of Suburbia
I love that album, and I love that song, but that last line in that verse gets on my nerves! Of course, it it about graffiti, which isn’t always on board when it comes to proper English, and there is the whole interpretation offered by The Loaded Dog…
I have a few friends that say this and it bugs me. I keep wanting to correct them, but not wanting to be a grammar nazi, I don’t. I was born and raised on Couldn’t Care Less and it makes perfect sense to me. Could Care Less simply tells me that they do care which, in context, says absolutely nothing.
What bugs me is when it’s used with related phrases: I could give a rat’s ass and kin, for example.