I am surprised that you're surprised. It's not like Bitcoin was taught in school books, nor is it posted on every wall outside or every ad on the internet. It's like you're asking someone, "Why don't you know this game?" when they aren't even a gamer. If they were along the lines of developer/businessman, you can be half surprised since both have the chance of actually chancing upon Bitcoin. Besides, even the majority of the people who know about Bitcoin only know the word, they don't even know what it is.
He has every right to be surprised despite the fact that bitcoin was posted on every wall ads but bitcoin/blockchain are already among the brochure of some school in the US and it also easy for someone that gives graphic designer, dev, etc job online to know every mode of payment used online, so it normal for them to be surprised when his customers from the US said they are not an award of bitcoin.