The problem is our predicament. If God were to eradicate all evil He would have to eradicate us. The answer seems obvious. All of us have done things that are not right. The Bible calls this sin.
Sin is defined as falling short of the mark.
All of us fall short of the mark. We have done things that are wrong, thought things that are wrong, said things that are wrong. In short, we have sinned. In fact the Bible says that all of us have sinned and come short of the glory of God. This is our predicament.