Susan,

One of the main reasons society prefers that people hunt fowl with shotguns is that it's safer for people, property and those animals (including hunting dogs) that are not the objects of the hunt.

Shotgun pellets (compared to rifle bullets) are relatively small, not terribly aerodynamic projectiles. After a short distance, say a 100 yards or so for upland birdshot, they loose their speed and most of their capability to do harm. (Ask any experienced shotgunner if he's ever been "rained on" at a dove field or a public hunting grounds.)

Conversely, imagine a duck pond or lake, or a dove field, with hunters around the perimeter firing rifles at flying birds. How'd you like own property near that one? Or be within a couple miles? All those bullets gotta come down!

Also, it's comparatively earier to take a flying object out of the air with pattern of small projectiles than with a single projectile.

None of which makes wingshooting or "shooting flying" exactly easy. It is, IMHO, every bit as fun as handgun or rifle shooting, but an entirely different game based on nearly entirely different gunning skills.

Mark