Real gunners did not have a 1000 hours of practice either and had far more distractions to deal with.
P.S. If you ever find me flying a bomber in the game, I am easy prey. I cannot hit the broad side of a barn with a basketball, much less shoot down a moving target.
That may be true, but there is more to it.
To aim the guns, the gunner needs to align his eye, two points along the gun and the target - and keep them aligned while aiming. That is not easy at all, especially if there is another degree of freedom and the gun itself can move freely (like the held MGs of the waist gunners). When the plane vibrates and hops on turbulence, the head bobs and so does the gun if it is not fixed to the airframe. I did the experiment of trying to shoot out of a moving car once - I couldn't hit ANYTHING, even when driving at just 20-30 km/h, unless it was very big in angular size (i.e. either very close or very big in dimensions). Just to keep the eye, rear and front sights aligned was no simple task. In the game, the reticule is always perfect - the bullets will fly where it points and my eye is always looking down the aiming line - no matter what the plane does or if I swivel the gun around. Gunners in AH have a perfect aim even if the plane is diving at 500 mph or pulling a 5G turn.
In addition, shooting at any direction which is not straight forward/backward is like shooting through a cross wind of the scale of a hurricane. Shooting at a plane flying perfectly parallel, the gunner has a cross wind of 200-250 mph. If the target is not flying perfectly parallel, from his point of view it is now equivalent to shooting at a moving target with a 250 mph cross-wind. To put it in perspective, this means a drift of about 100 yards per second of bullet flight-time. In AH the air is absolutely and perfectly stable, and bullets do not tumble if they come out of the barrel and meet a 250 mph wind sheer, nor do they meet any turbulence from the plane, or any variations in the airflow over a distance of 1000 yards to the target. Finally, in shooting through a cross wind, range estimation is critical. The ranged icons in the game help a lot in that respect.
AH does as good a job as any in including the scatter inherent to the gun and its installation. Ignoring the issue with holding the eye to the gunsight is a sensible gameplay concession because except for the track-IR 6DoF users, other players have very limited and awkward control of their head position. The only way to simulate vibrations ruining the aim is to add some additional random scatter to the guns and I am not sure that this is the right thing to do. Detailed atmosphere and its effect on the bullets is probably too much effort for a minor benefit, so I see the reason in not even attempting it.
My original comment was not a criticism of AH, it was about the value of gunners in WWII bombers. I really think that they were next to useless, especially the gunners in more maneuverable aircraft like the Me110, SBD, Stuka, IL2, A20, etc. The main thing that gunners added to the heavy bombers is a higher death toll. That is just my opinion.