Don't know the full reason or details Curly but our Graham will tell you when he sees the thread.
Normally they use a DACS box to take advantage of the existing line already coming into the property to split the line into two separate lines, either for yourself or for you and your neighbour. Saves having to run another cable from the pole to the property.
At my previous address about eight years back they asked if they could do this from my line by splitting it where it entered the house and diverting it next door. I said no. The Pole was only 25 metres away at the bottom of the garden!