Ill on a train, again

Tonight there are "severe delays" on the Met and Circle and District and Hammersmith, due to a person "taken ill on a train" at Great Portland Street. I've written about this phenomenon of tube train operations before and am still confused. If someone is ill, surely you get them off the train as soon as possible. There are first aid facilities and trained staff at each station. Why should the, undoubtedly regrettable, illness of a passenger create severe delays? Minor delays perhaps. But this smacks more of a knee-jerk reaction by the Line Controllers. What? - someone has lightly bruised their upper arm on a seat support?! – help, panic, cancel all trains, close the barriers, update the website, and where did I put that headless chicken mask?

update: I wrote the forgoing just before leaving for home. When I reached Baker Street the announcement had changed. Now it was "a fatality" that had caused the problem. Well this makes the delays totally understandable, of course. And now we know that "ill" means "dead" in Tubespeak.