When you get on a Southeastern or Southwestern metro trains, they often utilise the full 30 seconds before departure to close the doors and often have lead to leaving the platform 15 seconds early. (If you look on RTT at Waterloo/London Bridge, often many of them are 1/4E departures)
Given the advance in door closing technology, there seems to be no need to have 30 seconds to close doors which at the end leads to waste of time in long dwelling at the next station early.
Of course, not to mention, seems the UK is the only county close the door before the scheduled departure time, at least not in EU, Japan, Taiwan or other east Asian countries. It is not a customer friendly approach.
Given the advance in door closing technology, there seems to be no need to have 30 seconds to close doors which at the end leads to waste of time in long dwelling at the next station early.
Of course, not to mention, seems the UK is the only county close the door before the scheduled departure time, at least not in EU, Japan, Taiwan or other east Asian countries. It is not a customer friendly approach.