Apparently vanilla ice cream is not a fan-favorite in the U.S., as “vanilla” is used to describe someone or something that is ordinary, boring or uninspiring. It serves a similar purpose as “basic”, although at least “basic” has the distinction of implying someone is a slave to mainstream trends. “Vanilla” doesn’t merit that recognition. Just as vanilla ice cream is seen as a very normal flavor, a “vanilla” person is someone with a plain and unexciting personality.