Rivalries create continuity
A season is easier to follow when each week connects to an ongoing story. A rematch, a disputed trade or a championship loss gives ordinary regular-season games context.
They create reasons to communicate
Managers who have a rivalry are more likely to check scores, send messages, notice injuries and watch a Monday-night finish. The social layer turns passive roster management into an event.
They make small leagues viable
A two-manager league does not need twelve different personalities to create drama. One opponent is enough when the competition is meaningful and the history is visible.
They produce shareable moments
Close finishes, weekly stakes, victory messages and punishment outcomes naturally become stories people can share outside the app. That is useful for both league culture and product growth.