@gpvos - That doesn't always work. Sometimes a train will arrive early, but another train is scheduled to arrive before them, so they have to wait until the other train arrives and departs before they can enter the station, or they'll screw everything up. The train system in Japan isn't a single-line system, like the ones that exist in many cities. It is extremely complex, with express trains and trains that stop at every station all using the same platforms. The arrivals and departures have to be precise for the whole system to work.
Well yeah, I'm assuming the platform is free. Otherwise the train has to wait, obviously; that's the way it works in most places.
Is the platform guaranteed empty during a time when a train is not scheduled to be there? It seems to me there might be a lot of benefits to knowing that a train is either going to be there or not. Having a system that runs on time, and then having trains arrive when they are not supposed to is not necessarily an advantage.
An arrival jingle plays when a train arrives. If it plays early, people are going to rush thinking they're about to miss the train.
It's better to arrive exactly on time.
Well, that's silly too. They should play a separate pre-departure jingle 30 seconds or whatever before the train is expected to depart.
Hmm, I can imagine that having the jingle play automatically on arrival is easier and more robust to implement (no further human intervention needed) than your proposal. So that is a somewhat reasonable explanation.