Just to be disgustingly credible for a moment, I imagine that the biggest practical issue with tethering a drone to, say, a tank, is that as soon as someone spots the drone (which is floating in the air with zero ability to camouflage itself) they have now spotted that you have a tank somewhere very close by. Close enough that just dropping an artillery barrage on the whole area probably isn’t a waste. With good enough optics you could probably even follow the cable in order to get an exact location on the operator, and then introduce them to Mr Missile.
Just to be disgustingly credible for a moment, I imagine that the biggest practical issue with tethering a drone to, say, a tank, is that as soon as someone spots the drone (which is floating in the air with zero ability to camouflage itself) they have now spotted that you have a tank somewhere very close by. Close enough that just dropping an artillery barrage on the whole area probably isn’t a waste. With good enough optics you could probably even follow the cable in order to get an exact location on the operator, and then introduce them to Mr Missile.