Why were rashaim created?. The same could be asked of tzadikim. Of anyone in fact. Hashem knows what will transpire, so He can skip the whole process of giving anyone life.
Without rejecting aforementioned responses, I would add that the experience of living a life is important to the soul. Though we know in advance with reasonable certainty that a child will enjoy an outing to an amusement park, we bring the child anyhow. Or, we know a criminal will suffer in prison, but we lock him up anyhow. In both of these examples it is the experience itself that makes the difference. (For the sake of my argument, I am excluding cases of protecting society.)