Paris is still hanging around hoping he can marry Juliet.
Unfortunately, Juliet's still way depressed about Tybalt/Romeo.
Of course, her parents don't know about the Romeo part, and Juliet's grief for Tybalt seems so extreme to her father that he changes his mind about waiting a few years before she is married. What better way to cheer her up than to force her into a marriage with a man she's just not that into?
Figuring that there's no way Juliet could refuse a great guy like Paris, Lord Capulet decides to go full speed ahead. How about marrying her next week? he asks Paris.