The huge difference is the shooting range. Sound is inversely proportional to the square of the distance, so there is 4 times the sound that a deer hears at 25yds vs. 50yds. Scent is also a much bigger factor at close range. With a bow, you must draw back, and this is often when you are busted. Compare to lifting rifle slowly to a rest.

And as mentioned, bow season is a lot more peaceful than the gun season. For some, that is the biggest factor.