Where did that come from: "I could(n't) care less."

Regarding the conundrum that is I could care less versus I couldn't care less.

An excerpt from World Wide Words:

" The form I could care less has provoked a vast amount of comment and criticism in the past thirty years or so. Few people have had a kind word for it, and many have been vehemently opposed to it (William and Mary Morris, for example, in the Harper Dictionary of Contemporary Usage, back in 1975, called it “an ignorant debasement of language”, which seems much too powerful a condemnation). Writers are less inclined to abuse it these days, perhaps because Americans have had time to get used to it.

A bit of history first: the original expression, of course, was I couldn’t care less, meaning “it is impossible for me to have less interest or concern in this matter, since I am already utterly indifferent”. It is originally British. The first record of it in print I know of is in 1946, as the title of a book by Anthony Phelps, recording his experiences in Air Transport Auxiliary during World War II. It seems to have reached the US some time in the 1950s and to have become popular in the latter part of that decade. The inverted form I could care less was coined in the US and is found only there. It may have begun to be used in the early 1960s, though it turns up in a written form only in 1966.

...Taken literally, if one could care less, then one must care at least a little, which is obviously the opposite of what is meant. It is so clearly logical nonsense that to condemn it for being so (as some commentators have done) misses the point. The intent is obviously sarcastic — the speaker is really saying, “As if there was something in the world that I care less about.”

... There’s a close link between the stress pattern of I could care less and the kind that appears in certain sarcastic or self-deprecatory phrases that are associated with the Yiddish heritage and (especially) New York Jewish speech. Perhaps the best known is I should be so lucky!, in which the real sense is often “I have no hope of being so lucky”, a closely similar stress pattern with the same sarcastic inversion of meaning. "

I personally cringe when I hear people say "I could care less." And I don't buy the intentional sarcasm theory either. It's just not thinking about the logic of what you've just said. If you could actually care less...then what's the point in emphasis? Ignorant debasement of language, or just spoken without thought? Am I being an ass?