Once, orcs were the terror of the North. Breeding rapidly they would congregate in gargantuan hordes, looting and pillaging everything in their path. And as to be expected, when Negroth the Doombringer needed armies for his invasions, the orc tribes were all too willing to heed his call, hammering against the armies of the Flannish Cities until they were routed. Then they indulged themselves on Negroth's conquests, including scattering their seeds among the terrified populace.
But when Negroth was killed at the Hollerpass, the tribes immediately began to fight each other for leadership, making the remainder easy prey for the vengeful humans. In the end, only few stragglers escaped back to the Norfjell Wastes (although they did take some price loot with them which in some cases remains as tribal treasure to this day). All the while the armies of the Hobgoblin Dominions swept through the wastes, putting every orc they could find to the sword - including the elderly who were the upholders of the tribes' traditions and the children which were their future.
It was a blow from which the orcs never recovered. While new tribes formed eventually, they were rife with conflict and paid little heed to the humans slowly spreading through their lands. Those who fought were eventually wiped out by the invaders, who proved to be more tenacious in the end. Those who retreated had to venture deeper and deeper into the wilderness where food sources became scarcer and scarcer. And so most orc tribes remain to this day - eking out their existence in the harshest of lands, their high fecundity more than balanced by the ever-constant threat of starvation. While they still remain a threat to small, outlying settlements, the time where they can threaten the mighty city-states of the North is long past.
Not all orcs are willing to remain with the tribes, however. Some have found that they can survive by doing business with the more criminal elements of human society. Smuggling, piracy on the Great Lake, the slave trade - all of these offer plenty of opportunities for orcs willing to break with tradition. Even the Flannish Cities are seeing an increase in orcs who work as enforcers (and rarely, leaders) for criminal organizations, where their strength and reputation work well for them. Also increasing, but far rarer still, are the orcs who attempt to make a honest living as common laborers - a task for which they are paid far less than any human at the same job, which causes many of them to revert to criminality.