Whenever I see a situation where players just won't up a fighter it's because they can't even get to the point of gear up before a fast mover is coming in behind them and a turn fighter is swooping in from one side. If the goal is to set a virtually unbeatable cap over a field, where there's a giant wagon wheel of aircraft 2-6K above, then I wouldn't up there either, I'd launch from another field.
Sometimes I think people have unrealistic expectations with their ideas of what a "fight" is. If they set the conditions up to be nearly unbeatable, they shouldn't complain when no one wants to spend time being their bullet sponge. I'd suggest backing off a bit, or spreading the planes out more if no one is upping. There's no need to have 9 planes over a field waiting for one guy to take off, then not even allowing him to get to takeoff speed before drilling him - unless the goal is total suppression of the field and if that's the case, no uppers = good news.
If it's only one or two planes, it depends on the planes and what they're doing. Too many times I've seen someone in a 190D come whistling in with a lot of smash looking to stir something up and do nothing but climb to the point of stall, rinse, and repeat. Soon as I can get enough alt to actually have a fight, they wep the heck out of there. So if I see a 190D doing that, I don't waste my time. Let him shoot up the fuel tanks or whatever, odds are he'll only fight as long as he has a major advantage and will run away fast if they lose it.
I know some don't do that... we've had some good fights, some I lose, some I don't, but too many do that runaway thing after enticing me to up and fight. So for me, depends on the plane and what's going on.