We don't. Even the tiny number of people that do their own butchering rarely mention it. I've had hunters tell me "don't give bones to your dogs its bad for them!"
Most Americans don't know marrows could be food and would probably have to be starving before they'd try it.
I've lived in North Carolina, Virginia, Ohio, Texas, New York and Colorado.... Wherever you happen to be I'd guess that if you start looking you'll find that it's always been there.
I've had pork bones break in scary ways as well when the dogs got into them. I personally don't give my dogs anything but rawhides and large beef bones anymore, both of which you just have to buy specially really.
On the subject of actual marrow, it adds a lot to soups and stews. Usually added via just cooking the bones in the soup/stew and removing towards the end.