Another factor to take into account is the element of surprise
Luftwaffe ace of aces Erich Hartmann is quoted as being confident that eight out of ten aircraft he shot down never knew he was there before he opened fire, while US P-38 pilot Mark Hubbard stated that "90% of all fighters shot down never saw the guy who hit them"
The cockpit of a single-seat WWII fighter was a noisy and uncomfortable space to function in and actually flying and navigating took up a lot of the pilot's attention
Stressful and frequent combat missions compounded fatigue to the extent that tracers flying past his canopy were often the first indication a pilot would have that he was being targeted, and even then they might not be noticed until rounds actually started striking the airframe
In these ambush scenarios, by the time evasive action could have been taken it would often be too late