'Bill Gates will give a nickel every time this is read' (remember email chains?), 'naked women get shared, but this heroic child won't get a single like', 'Like and Share if you stand with politician X', etc etc.
Combine this with the targeted scamming of elderly from various Nigerian princes and jailed grandchildren, and there does seem to be a much greater degree of credulity with our current elderly generation. I think a more interesting study would be to figure out whether it's generational, a function of changing brain physiology as we age, or what.