Because all colonies had to agree.
Wait, who lived in that time? The answer could be 'war' but I need more information...
The answer to this should be: A sizable middle class has developed.
With a middle class they can create a better governance; The Middle Class has a strong interest in promoting foresighted policies and making government work well because their economic fate is more closely tied to the quality of government than that of the wealthy.
Hope this helped :)
Have a great day
