The site is the largest heavily fortified site in Europe known from that time; it’s a reasonable guess that it didn’t get built so sissy inhabitants could cower down behind the walls when their more powerful neighbors came in. As with the somewhat later Mycenaean sites in Greece and at Troy, the high-walled citadel was the stronghold from which a city-state was ruled, and that most of the habitation was outside the walls, iow, not yet identified and excavated. Fortification goes hand-in-hand with agriculture. You need someplace secure to store the harvested grain, and other wealth of the area, so wandering bands of barbarians cant just raid you and carry off your food supply.