I suspect that every state had a unique set of considerations but that the thinking behind the shotgun only decision. I also think that what the agricultural states did was pretty consistent given that they all tended to have the same lack of forest lands and very low herd numbers when the shotgun only decisions were made..
In New york where for many years rifles were legal in the Adirondacks and Catskills but not in most of the rest of the state the decision had to do with hunter population density, open rural terrain and the size of the deer herd but was focused on deer survival far more than on safety. They knew that a lot more folks per square mile would be hunting in the agricultural "Southern Zone" areas than in the more heavily wooded and less populated mountainous areas. Smooth bore shotguns with the Foster slugs that were the then state of the art in single projectile deer loads were so much less capable than rifles that they were mandated in much of the state to ensure that a deer breeding population survived at a high enough level to enable both herd survival and increase.
Like many other states, New York forest lands were often clear cut whether in agricultural areas or not. The Great Depression and WWII caused a lot of folks to leave marginal or worn out farm land and in New York millions of acres of that abandoned land became state forests and parks. New York, like some other states, now has more than twice the forest acreage than it did in 1900. The deer population is so much larger today that while the total deer take in1900 was 4,800, in the early 1940s was still below 20,000 it now runs around 200,00 per year. For several recent years it was near or over 300,000.
As the deer herd increased seasons and harvest limits were expanded. New season were added. New implements were added and newer technological advances were incorporated. In all "shotgun only" areas you can use rifled shotguns (an oxymoron if ever there was one) and can use pistols-including those chambered for rifle cartridges, bows-stick, recurve and compound bows and muzzleloading firearms including in-line ignition, scope, smokeless powder rifle etc. Last season was the first season in which crossbows were added in much of the state although in a limited fashion.
Despite all these changes there has been a continued increase of the deer herd and large areas once closed to rifles have been converted to areas where rifles are legal. That is happening on a county by county basis and the new wrinkle is the increasing parcelization of rural areas and the attendant perception of it being a safety issue.
In shotgun only areas that allow the variety of implements that New York does or that allow rifled shotguns or in-line muzzleloading rifles at all you really cannot make an argument that rifles are somehow less safe than shotguns or other currently legal implements. In fact, I think that when facts are used in a discussion it is pretty hard to argue that smooth bore shotguns are somehow more safe than rifles in the conditions under which we actually hunt.
Lance