Cities change and people move around. The need to monitor and understand these changes has increased as cities have become more vulnerable to traffic surges and anomalies. With an efficient IT infrastructure you can continuously monitor passenger flows, their behaviors and use this data to more efficiently set up transit routes with optimal placement of bus stops and train stations.
Most ticketing methods are insufficient to truly estimate passenger flows, especially in urban settings. They can be used to record passengers getting on board but not getting off. Statistical data for boardings and alightings is essential in the design and planning of public transport. You need to know both the real origin and the destination of passengers.