Lack of frequency? What are you suggesting....6 times a day to long-haul points? I would have thought that minimum 4 weekly up to 2 daily would be the required amounts for each destination. Obvsiuouly, New York is different as we have 3 757s and a 1 767 each day.
Lack of passengers? Better tell Emirates that then as they must be completly potty to have decided to go from 2 weekly A310 via FRA to 2 daily non-stop 77W as there are apparently this perceived "lack of passengers" wanting to fly.
What might be the problem for most airlines is that there is a tremendous number of passengers wishing to fly out of the regions on long-haul routes but to service them means that inappropriate aircraft and/or configurations would have to be used. If there were multiple destinations (5 to 10?) where a general profile mix of 15% to 20% business class with the rest economy then airlines might find it more economic to develop a mini-fleet configured that way. Where some people go wrong is to always compare MAN with LGW/LHR. THere is no way that MAN would ever be able to attract the yields they do....I would like to think that MAN could raise yield levels to those comparable with MUC.
I find it mildly interesting that BA complained about the proposed introduction of extra services to New York in the late 1980s as the market "wouldn't sustain 2 carriers" which I would have thought everyone taking to mean that BA would withdraw their service, yet they still plod on after seeing off AA and DL in the 1990s.