Why Was it necessary for Greece to establish colonies?

In a pre-television age, the Greeks filled in their evenings by breeding prolifically. As each Greek city-state had very limited land, and each family had just enough for subsistence, it was not possible to split it up amongst several sons. So the surplus population was periodically shipped off around the Mediterranean and Black Sea coastlines to seize land and form new city-states. This ended up with over 2,000 cities spread from Massilia (today's Marseilles) in France and Tripolis (three cities- today's Tripoli) in Libya in the West to Asia Minor and southern Russia in the East.