The Montegues are having a party and anyone that is not a Capulate can come. They also then see that Romeo has a love but he thinks he should give up on her because she will never love him. So half of the dialogue for the act's are them throwing a party and discussing a love.

As a writer I still see this as a modern day clique or gang. They are having a party over something current and they wont let anybody from the other faction in. Then when Romeo discusses his love it would be a girl who has strict parents or something.