If you leave work at 6pm and want to take the train at 6:15 to get home at 7, including one change of trains, and your train has 15 minutes delay, you miss the connection. Then you have to wait for the next train, which might be an hour wait. Then that train is delayed by 20 minutes and you get home at 8:30. That’s the real problem of the delays.
That doesn’t help because the connections are planned to be meeting this train at the planned time. They plan the trains so that you can move from one to the next to reach your destination. And they know who is on which train and sometimes they’ll delay a connected train to get everyone aboard. But that’s rare and you can’t plan for shit like that. And if your plan is to count it as a 6:30 train, your 45 minute commute turns into a 2h+ commute. At that point, I’d buy a car.