Is guessing not attempting?

A post from our good friends at the Freakonomics blog describes a teacher who subtracts a 1/4 point for wrong answers, but gives 1/4 point for answering "I don't know" (full text below). I think I understand the reasoning but to me it feels like a reward for quiting. Do the benefits for knowing when to say IDK outweigh the confidence one can get from attempting and succeeding at something risky? I think no, but I don't know.

"In my classroom, students lose 1/4 point for wrong answers on quizzes. But for writing “I don’t know,” they get 1/4 point. (A correct answer is 1 point). The rationale is that if someone is in a medical emergency, and someone asks me what should be done, the answer “I don’t know” is much preferable to a guess. “I don’t know” leads the questioner to ask someone who hopefully is knowledgeable.
Part of why “I don’t know is so hard to say” stems from an education system based on attempting every single question, whether you know the answer or not.
P.S.: End-of-year student survey showed students strongly supported the +1/4 point IDK and -1/4 point wrong-answer system."