It's the coordination work. Project management, accounting, purchasing, compliance, etc, is about figuring out what the hell is going on, and what the hell should be done. When an organization reaches certain thresholds of complexity, a lot of labor needs to be spent on those kind of activities, or else the whole operation of the organization seizes up.

The day to day varies, but spending all day updating spreadsheets and sending emails is common. A lot of them are bullshit, and only exist to fight fires that other parts of the organization are lighting. Many are complex and require extensive training to do, but most can probably be done by someone who just lied on their resume. They are physically cushy, and often pay better than manual labor or standing-up jobs (but not always, especially not the ones that don't require any credentials).