<human>: This is basically the question asked by my high school students today. I asked the class if anyone knew where the expression "turn a blind eye" came from? Not only did nobody know where it came from, not one student had even *heard* of the expression. I was a little concerned and asked if they knew other common expressions like "don't count your chickens before they hatch" and "the straw that broke the camel's back." Again, nothing. When I explained the expressions and the proper context for using them, they questioned what is the purpose? Why not just say what you mean to say? The only way I could think to explain it was that in writing and speech, you don't always want to flat-out say your point. Again, they were puzzled as to why you wouldn't. In a word of "real talk", what's the point? Are expressions fading from today's youth culture or is this normal?

Can you condense the text into a few key points?
<bot>: Surprised by the number of high school students (mostly juniors) who not only never USE expressions, but don't even know the most common of them.