They don’t fly -they’re tethered to their ground control station.
They may be tethered, but they are still subject to weather conditions. High winds play havoc with the tethers, attachment points and anchoring
Yes like the barrage balloons during the second World War. But they don't do well in say strong wind, snow or icing conditions. Never mind that they will be a rich target for any bored hunter with a high powered rifle.