The reality is that Turkish Airlines is on a ridiculous quest to be the biggest & fly to every country in the World (they already fly to more destinations than any other airline, even if some are pretty pointless, not required or war torn - Mogadishu, not Glasgow).
The point is, any other National airline in the World probably wouldn't dream of servicing Scotland, they'd do the sensible thing and stop at Heathrow or Manchester at a push. To have a service to Scotland at all is a miracle, provided only by the egocentric wastefulness that is TA.
Although it would obviously never happen, if KLM, BA or just about any major airline took over TA, such routes would be chopped on the first morning - so enjoy the very fact they fly to Scotland