Price is part of the equation. BA tends to have more seats in F than their competitors (depending on aircraft type and competitor more than double), which allows them to milk the maximum on direct routes (think >£10k) and then sell the rest cheaply to connecting traffic (plus of course the various GUFs & POUGs). For the core target audience (not very price sensitive but focused on convenience and comfort) that works very well - a lot of rich people want to travel between London and the world. A connection in Frankfurt (even if it is a Porsche aircraft to aircraft transfer is probably not what these people consider ideal).

Unfortunately that model means that BA can get away with an inferior product (people value the no-stop element over caviar), and the high number of people on cheap tickets give further incentive not to invest.