For example rush hour is an emergent phenomenon. But it's something that is happening pretty regularly depending on typical work schedules. You can simulate thousands or millions of agents with their intricate goals of their daily lives to have it emerge naturally (and it's very fun to program that), or you can just hardcode fixed times for rush hours. In a big-picture view of country-wide statistics the difference between these approaches is underwhelmingly small.

It's sort of like simulating every atom of an object vs using Newtonian physics. There is a difference in accuracy, but it may not even become apparent or matter for gameplay.