Is to say "why not" same as to say "why?"

Native speaker’s answer
Rebecca
Yes, it does have the same meaning. It just sounds more natural if someone has pointed out that they're not doing something or don't want something. The negative follows the negative. As if asking someone the reason why they DON'T want to do something. But you could use either "why" or "why not" here. Ex: A: I'm not going to visit her anymore. B: Why not? = Why? Ex: A: You shouldn't be mad. B: Why not?