Answer:
There are several reasons to this: economy, laws, politics.
A peaceful settlement wasn't possible because differences were critical. As colonies, they must pay 'high taxes' to the crown, and British Empire wasn't able to quit to that money, because colonies purposes, from the beginning, was to maintain crown's power and economy.
Also, colonies had laws that limited them in so may ways, they weren't as free as the people in Great Britain, but they paid high taxes to some government that never visited their lands.