I have spent a good deal of my career working with the Corp as an industrial rehabilitation contractor working on dams including the Table Rock Tainter Gate rehab project well over a decade ago. As Phil said, the hoist motors are super expensive.
The primary mission of the USACE related to dams is NAVIGATION, not flooding and certainly not power generation. The mission is defined by Congress and maintaining navigable waterways for national defense & economic purposes is top priority. Preventing disasters that endangers people (Voters) is next priority. Beyond that, the priorities may differ based on what they have agreed and contracted to do in that district.
Remember the whole organization is part of the US Army and is run by Army Officers. All of us veterans are familiar with the right way, the wrong way and the Military way.
Federal Environmental Regulation, Endangered or Threatened Species Acts, Wetland and Migratory Bird Habitat Preservation agreements, Agricultural & Industrial water contracts, etc, can all play into the water-flow equation.
For example, in Kansas a certain volume of water is required on Redmond Reservoir as emergency coolant for the local nuclear power plant. On top of that, the State has contracted with the Corp and pays them to maintain extra water for use by agricultural industries.
Based on their mission parameters, the needs of the Mississippi River barge traffic and navigable portions of the White River will far outweigh what all of us want. Each district has Hydrology Engineers and some pretty sophisticated predictive software, so they aren't really guessing.
We just aren't important.