I always found it rather odd that just sitting in a station for too long was a death sentence. Can anyone give me good in-world reasoning behind the rule? I understand the game design reason, but I really don't get why it's explained like that in the game.
I'm not aware of an explanation for it in the text of the game, but I think the logic is there. It's not an analog to like, blocking the entrance to a parking lot. It's probably more like trying to blockade a bay city, or yelling "bomb" in an airport. Stations are cities, economic centers and military bases all rolled into one, and there's a lot that makes them vulnerable to aggression. "Loitering," or interfering in any small way with the traffic or operation of regular station activities by misusing your armed spaceship can be treated as hostile, even terroristic activity if it means the station is less able to defend itself.
Perhaps in-universe this lesson was learned early when some supposedly harmless, innocent citizen floated inside the entrance and blocked fighters while his pirate buddies buzzed the station and attacked civilians.
It's a harsh and unforgiving galaxy where death isn't very permanent. Loitering inside a station blocks the entrance or a landing pad, impeding commerce. Stations live on imports and exports and a blockade would kill residents. The easiest way to clear that blockage and keep commerce flowing is to destroy the ship that's in the way.
I think the game design reason is to help make stations a relatively safe place for "innocent" players, to make it harder to blockade stations, and to give you an automatic escape if you get stuck in some part of the station (like the rack around the slot).
Also, the voice message in stations is pretty funny and really sets a nice "harsh galaxy" vibe.
Lore-wise, it's not a death sentence. In fact, nobody ever really dies in Elite: Dangerous. So they're really not killing you, they're just getting you out of the way and making you pay your deductible. Still feels a little harsh, but it's not as bleak as it appears.