If they put stop orders in for other trains it would delay those passengers to. So by making you wait it helps try and keep the delays to a minimum. Lol.
Harrow was one they would miss out with the added bonus that London Midland and TfL didn't seem to like talking to one another so you wouldn't know about cancellations always. Don't know if things Ave improved since I stopped commuting there.
Delay minutes don't add up: a train with 500 people on that is 10 minutes late is 10 minutes late; a train with 10 people on that is 20 minutes late is 20 minutes late. The first train doesn't have more "lateness" because it's busier: an individual's lateness is not affected by the lateness of anyone else. Therefore, a busy train running a bit late should never miss stops if even a single person is made later as a result. I mean that right to it's limit, so every train for the entire rush hour out of Waterloo can run 10 minutes late if the alternative plan makes a single person 30 minutes late. Keeping delays to minimum only works at the level of a train not a person. The only rational reason for skip stopping is to avoid the sevice getting worse or collapsing because of people and trains being out of place.
You'll probably tell me I'm mad but, as I said, lateness is not something that is experienced as a group activity so all that matters to "me" is that any lateness is minimised.