Britain and France Disagreed on who owned the area
At that time the colonials had no need of a navy as they were part of the British Empire and could use the might of the British Navy for defense. However, the Ohio River Valley was a highway down to the Gulf of Mexico for the logging and fur trade. There were no roads in and out of the valley at that time and rivers were the best means of transportation.
The French who had control of Canada and they claimed the area from the St. Lawrence river down to the Ohio and the British claimed that the colonies extended all the way to the Pacific Ocean The war was for who had the better claim to the area and had the right to the large amounts of furs and resources.