Why did major battles during the american revolution take place in boston, new york, and philadelphia?

The Siege of Boston April 19, 1775 - March 17, 1776

(Lets also mention the Boston Massacre even though it wasn't a 'battle' 5 men were shot and killed by lobster-backs)

So New York had a heccing amount of battles but the most important ones were 'The Battle of Long Island' and 'The Battle of Fort Washington'

Philly was more importantly the place of the continental congress but I think the battle would be known as the 'Philadelphia Campaign' but it was less of a battle and more of military tactics