The British were the victors in the Seven Years War. Now that they were in charge of British North America, they had a problem. There were communities which held a lot of power which had no British population whatsoever. In order to gain complete control of the people, British settlers would have to move into those areas so that the british can control the vote.
The British wanted more English in Quebec so that they could control the population. However, the 13 colonies were the only group of British colonials they could manipulate and they were planning on expanding westward, opposed to northward. The Royal Proclamation gave the British an opportunity. By giving the land west of the 13 Colonies to the Natives, and enforcing the Line of Proclamation, they could prevent the west expansion and force the residents of the 13 colonies to travel north if they wanted to find new lands.
