Well, there could be several logical reasons for this phenomenon, so let me try to briefly explain a few potential scenarios:
1) Environmental conditions, such as heavy spring rains, growing season flood events, drought, and unusually high/low temperatures, can cause poor acorn pollination, acorn crop abortion, and complete acorn crop failures.
2) Early season frosts can severely damage oak flowers resulting in poor pollination success.
3) Some oak trees are genetically poor producers of acorns – absolutely nothing you can do.
4) Acorn production dramatically decreases when oaks reach a certain age and/or a certain diameter.
5) If your oak is in the red oak family, then you can typically expect heavier acorn crops every 3-5 years.
6) If your oak is in the white oak family, then you can typically expect heavier acorn crops every 4-7 years.
7) Pests or pathogens, confounded by weather-related phenomena, may also be responsible.
8) Past management or land-use history
Unfortunately, I cannot provide you a more definitive answer; however, I'm pretty confident that one (or a combination) of these factors has ultimately caused the lack of acorn production in your area(s).