Flight sims have to obey real laws of physics that many gamers have experienced for themselves, either as passengers or as pilots of real aircraft, so the game makers can't get away with simplistic or unrealistic control effects. Flight has gravity act in one constant direction and has the main lift vector always acting at 90o to the wing surface. Rates of pitch and roll are always far greater than yaw because aeroplanes rarely have rudder area anywhere near the area of the ailerons, elevators or stabiliators (as used on swing-wing airframes like Tornado, F111, F14, MiG23/27 etc). The amount of rudder authority has to be restricted on aeroplanes, too, in order not to upset roll stability - all control inputs on an aeroplane have primary and secondary effects, with roll and yaw interacting with eachother as their secondary effects.
Space flight sim writers have the advantage that few, if any, of us are personally familiar with space flight physics and dynamics, but also have the advantage that flight dynamics away from major gravitational bodies and atmoshere are much simpler - there is no lift and no fixed gravity point, just inertia. Flight controls will not have any secondary effects, controlling pitch, roll and yaw in perfect isolation. The "etheric rudder" effect, as Lucasarts calls it, linking yaw to a small amount of roll is a designer effect to mimic the movement we see in the Star Wars films, and that flight style was done because film audiences were familiar with aircraft movement but have little understanding of space flight.
In a nutshell, a space fighter would have rapid motions in all axis and would not have low yaw rates like aeroplanes, and the rudder would not affect roll just as roll would not affect yaw. Whether a hypothetical space fighter would have its roll axis controlled by stick and yaw by pedals, or whether the increased yaw rate and unimportance of would relegate rolling to a less useful manoeuvre controlled by the rudder or even a "hat switch" on the stick with yaw controlled by the main stick is open to debate. I suspect that since space pilots would likely be selected from the most capable atmospheric pilots (as we see with real space programmes), the traditional control configuration would be carried over - once pilots become accustomed to one set of controls effects, they will not want to have to unlearn those skills and acquire new ones. This is consistent with the controls on current space craft, including the Shuttle (though that does admittedly operate as an aeroplane for its late descent and landing phases).
