I keep seeing this phrase written as above, referring to people who have absolutely no interest in something. Surely it should be 'couldn't care less'?
Yes, it should be, but think Jewish and a shrug of the shoulders! It comes from America and should be in Yiddish. The community exists on irony and saying the reverse of what you mean; it lives on cynicism , too.
They have dogs too? The only Jew I knew with a dog was Bernie Winters, and that was only for his solo act, and tax deductible! I think the showers are goyim who have picked up this annoying phrase. They probably say "wake up and smell the coffee" too.