I have not read this passage, but one can infer the importance of such works. To have never known these aspects of human life, is to experience it all for the first time. When one has a first time experience, there is usually mixed emotions, so the speaker may feel this is important for the expression of these feelings. For example, if you have never been to a theme park before, what might you be feeling when you go for the first time? Excited? Scared? Overwhelmed? Thus, how is the nightingale feeling about these aspects of human life? This is important for reflection and description purposes.