The answer is simple. Learning curve. In Battlefield 2 you just get in and fly. Lomac - way different. I was scared by those controls at start.
If somebody made simulator/arcade mix that was easy to learn, it would be a hit. For example you can fly all the planes in "easy" mode, but in "advanced" mode you could have some advantages like long range targetting etc. Also simulator graphics suck. Simulators focuses too much on realism forgetting about fun factor.