We're seeing the cost of code drop dramatically and are facing the same problem in building new companies across most disciplines of, "what's a problem painful enough that someone will pay us to solve it?".
I suppose if we get to a massive enough scale we can effectively model every atom's interaction and human on earth's reaction to any stimulus but I think we're still some time off from that :)
In other words, you generate more training data by actually experimenting, just like humans do.