It changes risk decisions: instead of worrying only about safety the pilots/operators start to also worry about making the schedule. In the history of aviation,

It changes risk decisions: instead of worrying only about safety the pilots/operators start to also worry about making the schedule. In the history of aviation, it led to numerous accidents and incidents of pilots flying into bad weather, pilots flying un-airworthy aircrafts, etc. only because they've had schedule to meet.