Why is it necessary for scene 1 to take place in a public square?

This scene primarily sets up the conflict between the two houses and it shows the impact that the feud between the families has on the city at large.

First, this scene illustrates the intense hatred that the families have for each other; even their servants become involved in the fray!

Second, the Prince is able to break up the fight and establish a few ground rules

• this is NOT the first time this has happened--this is the THIRD time the families have started fighting in public, and both he and the rest of the residents have had enough

and

• this allows the Prince to lay down the "new and improved rules"--if there is fighting in the streets, whoever participates shall be put to death.

This, of course, comes into play in a later scene where fighting in the streets again occurs.