I can't speak for the very experienced players, but I and other less experienced players find it very hard to chemspray when things are already on fire. I guess if chemsprays are done correctly, nothing should ever catch fire, but a slight oversight or an occasional timing mistake can allow the flamethrower to put a gun-disabling amount of flame. In such situations when fresher engineers are panicking, it is essential that the pilot can maneuver the ship away from the fire and give the crew a repairing respite.
In my experience of piloting for MM crews, I found that its pilot's job to stay away from fires for misguided fire-extinguisher swabbies or fresh players unused to chemspray.
