I believe much of it has to do with the fact that guys with tacticool shotguns showing up on clay fields tend to pay little attention to rules of safety and etiquette.
Way to generalize people for what they shoot with. It is the person behind the weapon, not what the weapon looks like.... Thinking like that is why there are so many banned "assault type" weapons in many states today.
If you do a search for range accidents, I think you will find that the VAST majority of range accidents involve either the very young (a small child who steps into a firing lane) or the older 55+ crowd (who probably have those non-taticool, wood furniture weapons). I'm not trying to say something about older people, it is just that most of the times I see range accident reports, they usually involve someone who has been shooting for years and is up there in age. Is this due to experience complacency , diminished mental capacity, causing forgetfulness or just the law of averages seeing how they have been shooting for so long? who knows, but it is true.