I can think of 4 possible explanations:

1) Beechnuts are a turkeys #1 favorite Fall food. Some wildlife biologists will claim that turkeys even favor Fall beechnuts over Summer grasshoppers.

Could it be possible that the turkeys are beating you to the nuts, hence therefore you're only finding empty hulls?? Turkeys do not need to rip open the hulls to reach the nut, their beaks are sharp enough to usually pull the nut out by just reaching into the hulls crack. Squirrels are also pretty efficient.

2) There is a disease, Beech blight, similar to Elm disease. This is usually evident by distinct off-coloration of the trunk (you can usually detect whitish "spots" or streaks). If the trees are diseased, the end result could be reduced fruit production. I've seen this in upstate NY, but usually 2/10 trees still produce a large amount of ripe fruit.

3) Another possibility is the natural pollenator (either a bird or a bee, I'm not sure which for Beech---I'm pretty sure it's not a wind-borne fertilizer) could be lacking in your area. Hence, the flowers are not being fertilized, resulting in the production of empty hulls.

4) Finally, is the beech grove in an area with a low water table, or have you experienced drought conditions. In years of drought, mast productions historically are very low, as most of the water is spent for simple "maintenance" with little left over for reproductive capabilities.

S&R