Recently, a conversation has been happening on social media. That conversation is that women shouldn't have to say "I'm taken" or "I have a boyfriend/fiancé" in order to rebuff a person hitting on them. A simple "I'm not interested" should be enough. Apparently "I'm taken" implies that men own women and the only way a man will back off is if the woman is a possession of another man.
Now, of course, there are no absolutes. Each situation must be taken in its own way.
However, stating "I'm taken," is the quickest way to shoot down unwanted advances. It is likely also the safest way. If a woman says "I'm not interested," it opens the door to being asked "why?" or worse: "you bitch," followed by a roofie in your drink.
Honestly, we women are saving men's egos when we say "sorry, I'm taken." It may carry connotations of "if I wasn't taken, I'd totally flirt with you right now," but so what? Shoot down the conversation and move on.