Because on the SE suburban network all services are different. On the North Kent Line southeastern go to Cannon Street via 2 different routes, one of which is a circular service which has to line up with all the timings from the Bexleyheath line.Why can't South Eastern have regular say 10-15 min gaps in the timetables like over on Southern/South Western instead of the larger 20-30 min gaps? It seems like that SE suburban services are the poor relation of the three railways south of the river.
etc etc etc it’s too convoluted