It escaped some closure plans in the post Beeching era (remember there was decent freight to Waddon Marsh Power Station in those days which would have retained the line for freight only) , - there was deemed to be some hardship / diffuculty in providing alternative bus options. BR just ran it as cheaply as it could. It was closed to facilitate greater things - the present , brilliantly succesfull , tram service. I played a modest part in persuading FCC to give up the 4 car bay at Wimbledon to support the recent track changes and increased service spec. As you guess, I was a local resident and railway man for some years.