This seems to be a golden year of new services to Manchester with growth across several markets (beach, city, long haul, low-service, high-service) and yet the old "why won't British Airways be my friend" rants are in full force.
BA are a business and have decided that their profitability can best be achieved through focused resources and channeling people through their hub in Heathrow (and to a lesser extent, Gatwick). As others have pointed out, this is no different from most European majors (even Lufthansa are moving this way in a far more decentralised country).
MAN is obviously doing something right, as it has a hugely diversified airline portfolio and I've no doubt this success will continue. However, the "London Airways" chip-on-shoulder rants are tedious.