The Declaration summarized the colonists’ motivations for seeking independence. By declaring themselves an independent nation, the American colonists were able to confirm an official alliance with the Government of France and obtain French assistance in the war against Great Britain. So basically so it could be official
They wanted to stay nurtral to make more money.
Paine, along with many revolutionaries of the period, viewed government as being inherently limited, in the sense that it was meant to serve the people and not the other way around. That's why he wrote "common sense" which talked about the absurdity of British rule over the colonies.
