God allows evil for a season, for a reason.
I believe there is much more to this than we realize, and it all has to do with human nature.
For a time, I had the same objections that rubliw and SGT have expressed. Why would God permit evil to exist, especially if He could make the world function just fine without evil? After all, if that is how He intended it, if we go by the account of Genesis, and one would presume that an all-loving and all-powerful God would want it that way, right?
Or... is that just human frailty speaking? Is it the same as the presumptions that Leftists make that the world ought to be a padded nursery wherein no no harm ever comes to anyone and everyone gets what they want? Is it just applying (however unconsciously) liberalism to matters of religion?
One thing I've noticed about life, something I'm sure many other folks have, is that hard times are good for the soul. Whether it be hard work teaching us about the value of responsibility and organization or whether it be times of financial difficulty teaching us how to appreciate simple things and a simpler life as opposed to a heavily materialistic outlook, humans often learn best when we have to learn the hard way. It's simply how we function; whether this is entirely by design of whether the introduction of sin into the world caused it somehow, the fact of the matter is that it is how things work as of the time of this post and for as long as we humans can recall.
Therefore, why should God immediately eliminate evil? God has given us all the tools to resist evil; He gave us consciences, He gave us the ability to reason, He gave us plenty of teachers and "prophets" who have expounded upon the topic of morality for centuries. If you are Catholic as I am, you believe that He gave us the Church as a moral guide. If not, you still can't but acknowledge the fact that humans have studied and refined our understanding of morality over the eons. Whether or not we adhere to it and live it out is one thing - but the fact that we have a highly-refined understanding of morality is impossible to deny. Why should God eliminate evil when He gave us the ability to defy evil every moment of every day of our lives? Why should God do for us that which He gave us the ability to do by ourselves? Did He create us for nothing?
No, God certainly doesn't "approve" of evil any more than moral humans do. But, God also gave us the ability to avoid evil; many moral exemplars throughout human history have lived as examples of this. If even one person can live in a moral, noble fashion, every human can do it. Yes, it's a high standard to hold each other up to, but a standard being high doesn't mean it is wrong. If just one Francis of Assisi can exist, a million of them can exist, and I don't mean merely in terms of charitable people. Francis was a highly moral man, and if he can be good, so can the rest of us, no excuses, because Francis was just a human being - born with the same mental and physical faculties we all were.
In a sense, evil can make good look better, because we understand much more fully how much good is needed whenever we see evil take place. But, we never need to let things degrade into genuine "evil" because we simply know that good is good because it is good, and if we need to, we can look to examples of it in the world to refresh our memories. Whether or not we approve of God's evident decision to permit evil to exist for now is immaterial; what matters is that we realize that God gave us all the ability to deny evil in our lives and prevent it from happening.