It took ~3 billion years of real evolution to reach Humans. This evolution occurred on a planet scale, including naturally formed barriers which rose and fell, changes to climatic conditions, and even a few stellar events to shake up evolution. There isn't even a compelling reason to think that Humans couldn't have arisen anytime within the last ~300 million years. Implying that the probabilities of intelligent life emerging are low, or that the conditions are poorly understood and rare.
Effectively each attempt to learn an agent which has to interact with the real world runs into these problems. The solution is to make the reward more complex and the simulated environment more realistic - both actions which increase the computational costs of the problem faster than the improvements arrive.