Bagso a million words when it's simpler.
If I fly CX MAN-HKG but the one single daily flight doesn't suit me, I can avail myself of one of the five daily LHR flights and connect on the way back or vice versa. The same should be true of SIN but non BA regional connections to LHR see the revenue flow to the long haul STAR partner and almost zero to the short haul one (BMI). Result being, service axed. I am off to LAX in the summer with American, going LHR-ORD-LAX-LHR, hence one of my flights is indirect. It's not uncommon and so your religious zeal that expanding the one hub we have can't benefit GLA, EDI, ABZ, LBA, BHD and MAN is to my eyes, palpably false.
Off topic but was through AMS yesterday, it's feeling incredibly old world and dated now.