Why do bad things happen to good people?

I often here Christians ask, "Why do bad things happen to good people?" I, honestly, am a bit confused by this question. Paul tells us that there is "no one righteous no not one". We are born with a sinful nature. We all have disobeyed God in thought, word, and deed. I think a more appropriate question is, "Why does God choose to have so much grace upon sinners."