Throughout history ordinary soldiers were often unwilling to fight against people from their own community. This often limited how authoritarian governments could respond to public unrest forcing them to accept reform or even leave power. Obviously they tried solving this by stationing troops far away from their home regions, creating various elite forces/deaths squads etc. But these all very expensive and/or required significant forethought.

Drones on the other hand are cheap and require fairly few people to operate. A few deaths squads in the control might be enough to suppress an entire country.