This may explain why we are not usually sensitive to our own smells-we simply do not need to be.
译文
这可以解释为什么我们通常对自己的气味不敏感——我们完全无需对其敏感。
点睛
why引导的是explain的宾语从句。破折号后的we simply do not need to be省略了sensitive to our own smells.是对之前内容的解释说明。