In order to do live performance, the directors often need to made a lot of cuts in order to shorten the story compared to the written text.
The first player's speech is important in order to put more emphasize on motif of the characters and how it is paralleled to the story. This will help the audiences understanding how a the characters behave the way they do throughout the story.
These are the basics. if you want more just look online
I think it is true. I can't really explain why though.
