First of all iambic pentameter is lyrical in nature and flows very easily making it easy to remember also its was a convention at the time within poetry (see Shakespear's sonnets) as well as plays. it is also less awkward then basis prose and sounds better this why many rap artist use this system today, remembering that Shakespeare in his day was not particularly highbrow it makes sense why he chose to use iambic pentameter.
It was basically the transitioning from the middle ages to the modern days with the 15 and 16th centuries as people lead different social lifes, buildings, writing, paintings, science, mostly just changing how society was.
