Target identification, threat assessment, determining level of force necessary, simply being a human face rather than a machine. Drones are also vulnerable to electrical issues, signal issues, all sorts of things a human simply doesn't need to worry about or are more easily remedied in a human.

Occupying land is not simply about killing the enemy, and multiple armies have learned this over the course of human history. Rarely are you concerned with SIMPLY taking the land - even if it's agrarian capacities or whatever you're worried about, having the employees still alive (largely) leads to better outcomes. Having a functioning economy in the occupied zone leads to less resistance. Facilitating the continuity of life within the occupied zone does too - and that doesn't work if your "occupation force" is a bunch of robot dogs that mow down anyone for being in the street.