Way way way back I used F3, when I was learning. It was very useful, for a beginner-learning-to-fight stage. I don't deny it makes things way easier than F2 mode, but you have to remember not everybody flies like you do. Some folks are just starting out. Some folks are stuck in arcade mode. Some folks avoid learning (see the EWA milk runners and fight avoiders, for example).
I think F3 has a place for learning, and sometimes just for fun. I don't know if it's worth having in the DA or not, but consider that you also go to the DA to learn how to fight, since you can't shoot an enemy down in the TA. Beginners are going to want to practice there, and they start with F3.
Maybe it's moot now. Maybe with private rooms you won't need them in the DA anymore. They'll have a room of their own with no fuel burn, no ammo limit, and F3 enabled. They'll go there and leave the DA to serious folk.