This kind of booing sound comes from the familiar live-audience tradition of publicly showing disapproval, especially at games, performances and comedy shows. Online, creators use extended boo clips as a quick shorthand for rejection or embarrassment, often in meme edits and sports reactions. It remains popular because viewers understand the joke instantly: a sustained boo says a moment went badly without needing dialogue. It also fits naturally beside other crowd-based reactions such as crowd cheering and the Sad Trombone.