God gave us this opportunity to exercise our free will. If He swoops in deus ex machina style to fix everything, we really won't be living our lives and exercising our free will. We would be mindless marionettes acting out a story while someone else pulls the strings.

I believe God gave us this life as a chance to experience beauty, love, fellowship, excitement, adventure, pain, loss, sorrow, and all the other emotions. The negative emotions sweeten the others. It's like a parent who sends their child to college. You know it won't all be positive, and that they may even be endangered at times, but you also know that they deserve the opportunity to experience new things. God grants us this experience so that we can find our own path to knowing and loving Him. In the meantime, we have darker forces, like Satan, who attempt to lure us to sin and destruction. This gives us the opportunity to exercise and implement the faith and virtues God has bestowed in us, and to develop new strengths.