Drone delivery is a pretty different thing. Drones are clearly visible to everyone. Submarines are... not that.
Speaking of which does Ukraine use weaponized RC vehicles and roaming unmanned anti-ship subs? I would think you would get a larger payload and better damage from the undercarriage.
Narco drone subs are delivery vehicles, just not for the “last mile” to the end user. They are more like self-driving long haul trucks that don’t care about international borders.