You have to ask (1) why does it still exist if it so bad and (2) shorthaul has often been shafted through management accounting transfers to ensure Ts and Cs remain low (namely of some LGW longhaul costs).
Gatwick is BA's loss leader and always has been. Long may it continue! Can you imagine the North Terminal covered in the dreaded orange?
Inventive accounting was always a feature of Lord King's tenure.
Gatwick has not made a profit since Airtours ceased to exist (RIP). In those days, also prior to the take over by BCal, the scheduled services made money. Anyone care to hazard a guess how if they don't now?
Ask a travel agent to book you from London to anywhere in Europe and I bet you don't get offered a flight from Gatwick unless every flight from Heathrow is overbooked by more than 20%. The marketeers seem to forget Gatwick.