In ancient societies, the economy was largely based on the land. In Attica, too, although what is usually emphasized is the part played by trade and workshops, it was farming that was of primary importance.
At the start of the Peloponnesian War, so Thucydides tells us, the majority of Athenian citizens lived outside Athens. Nor (he says) did this situation alter before the very end of the war (Thucydides, Histories 2.16.1). In 403, two thirds of all Athenians were still owners of land. It should however be emphasized that from an economic point of view they did not depend entirely on tilling this land. There were a fair number of well-off landowners investing, at this time, in maritime loans, real estate, workshops staffed by slaves, or silver mines at Laurion.

Until Athenian hegemony ended, an impoverished landowner could easily implement his income. He could take office as a juryman; or serve as rower in the Athenian fleet; or work as a labourer in the shipyards at the Piraeus or in the public civic rebuilding programme.
With the exception of jury service and service in the People's Assembly, all these opportunities to increase the income of poor families disappeared after 403 B.C. There was therefore no real reason for the people in question to migrate within the town walls of Athens. Once the income from hegemony was lost to them, the Athenians mainly relied on farming. To stay in farming country looked like a safer bet, perhaps. It allowed the penniless to find work - either as seasonal labourers or as farmers on land rented from powerful landowners.