Because I suspect that they would lose money hand over fist. I love Newcastle and its surroundings and most of all the people. However, I cannot think of many European countries where they do operate from two points. Germany (FRA and MUC) are one, and Switzerland (GVA and ZRH) on transatlantic flights - I do not think ITA fly from MXP on such routes. The much vaulted TK has concentrated everything on Istanbul as well.
Thus you are, unfortunately faced with either flying via Horrid Heathrow which is, in my very unhumble opinion, possibly the most dreadful airport to have to make connections - or KL. AF, and LH are very happy to fly you from NCL. I am just glad that I do not live there only because the dilemma would be what would happen were I to go to the Dark Side and fly AF? All my "Belta" friends on here would sit in their Belta BA Lounge and stick pins in my image. I could never listen to Brian Ferry again having cheated on him,
Cheer up - BA is regularly called London Airways on here and elsewhere.