Answer: Athens had a small population
Explanation: Athens as one of the city-states of ancient Greece did not have a large population, when compared to the entire ancient empire, or today's modern state. Direct democracy, as a form of democracy where all citizens take part in making political decisions, is possible in environments with a not so large population. These are practical reasons, because it is not possible to gather all the citizens of, say, some US states at one place to debate and vote on laws.