1) piloting a drone from a distance using the on board camera is much more difficult than it looks
2) dropping anything, but especially a thermite grenade requires the drone be almost on top of the tank
3) drones are LOUD and can be easily located esp on a quiet night.
4) many small drones do not have that great of a range 400 m and WELL inside the range of any soviet tank.
My thought was that the Ukrainians need something inexpensive to counteract the Russian armor and it’s evident that our Fearless Leader is not inclined to provide them anything except rations.