That's because not every single line is perfect iambic pentameter. Line after line of perfect meter ends up sounding more like a nursery rhyme than poetry, so poets (and playwrights) will play with the meter to emphasize certain words. Let's skip back to one of the non-perfect lines in the Prologue:
Hull is a town in Plymouth County, Massachusetts, United States, located on a peninsula at the southern edge of Boston Harbor. Its population was 10,293 at the 2010 census. Hull is the smallest town by land area in Plymouth County and the fourth smallest in the state.
Hull, GA Profile: Facts, Map & Data. Hull, Georgia - Basic Facts. The City of Hull had a population of 201 as of July 1, 2016. The primary coordinate point for Hull is located at latitude 34.0177 and longitude -83.2937 in Madison County. The formal boundaries for the City of Hull (see map below) encompass a land area of 0.32 sq. miles and a water area of 0 sq. miles.