Why were mobile animal herders not necessarily a threat to town life?

Mobile animal herders might take their flocks across a sown field to water which ruined the crop. They could raid agricultural villages to seize their stored goods. Sometimes herders were also denied access to river, by settled groups, and canal water along a particular set of path. There might be conflict. But mobile animal herders were not necessarily a threat to town life. They required exchanging their young animals, leather, cheese and meat for metal tools, grain, the manure of a penned flock etc. Through Mesopotamian history, animal herders of western desert filtered into the prosperous agricultural heartland. Such herders came in as herders, became prosperous and settled down. Some of them gained the power and established their own rule which include the Amorite, Akkadian, Assyrian and Aramaean communities. The kings of Mari belonged to Amorite community.