I think it's because the aroma of coffee is so important to its flavor.
My wife prefers flavored coffees and I shy away from them.
I thought I'd gotten them mixed or there was residue in my coffee maker because my coffee kept tasting sweet and I don't add sugar or use sweeteners at all.
Across the room was a candle in a jar, lid off, unlit, hazelnut coffee scented.
ACROSS THE ROOM it was enough to make me think my coffee was actually sweet. So yeah, it's all about the smell.