Junior year of high school a very popular girl I had known since elementary school informed her close LDS friend and me that her mother grew up as a Mormon but left the Church as a teenager after her mother died of an illness. She didn't understand why God would allow such a thing to happen.
I was shocked and saddened, first of all that this girl I had known for years had LDS ties, and second, that she could have lived a completely different life had her mother stayed true to the gospel. Her mother obviously did not understand the plan of salvation.
Unfortunately, she is not alone. Many doubt the existence of a God who allows suffering and wickedness and thus come to the conclusion that there is no God, or if there is, He is not the wonderful Being we believe Him to be.