How Can Anbody Not Know Who Sam Spade Is?

A younger crime fiction reader came across my reference to "Sam Spade" in one of my novels and made the comment they didn't know who he is. I thought my leg was being pulled, but the puzzlement was genuine. I was then just as flabbergasted, but I guess I assumed everybody knows about Dashiell Hammett's famous private eye creation. I didn't give it a second thought while I was doing the revisions of my novel. Name-dropping is always a dicey proposition in writing novels because of this very reason. Usually I refrain from doing it, but I figured Sam Spade has a broad, across-the-generations appeal and recognition. Probably not everyone has seen The Maltese Falcon film with Bogie starring as Spade, but the Sam Spade name must be used frequently and widely enough in the daily lexicon of English. I wonder if Philip Marlowe is also as unknown to any crime fiction readers. On the other hand, I don't know if Hammett or Chandler are on today's high school reading lists, so it's understandable why Sam Spade might be obscure. I remember I was assigned to read John Knowles' debut novel A Separate Peace in high school, but I think Hammett or Chandler would've been a lot more fun to me. At any rate, I'll certainly reconsider using the Sam Spade reference in the future novels as I'm writing them.