Fermentation is a great way to store excess food, which is why there's a ton of fermented foods across cultures. For civilizations centered around cereal crops, it makes sense that you'd see a lot of fermented cereal crops such as beer.

You can definitely see the benefit for an ancient civilization, since you're able to store many more calories which allows you to grow a much larger population base. But like many things associated with the move to agrarian civilizations, being good for the civilization doesn't necessarilly correlate with being good for the individual.