Why don't they use helium balloons for quadcopters?

Question

Microcontrollers

The whole point is in the question, I wonder why they don’t use helium balloons to reduce the weight of the unit, because then it will spend much less energy on maintaining it in the air and, accordingly, fly longer, are there any problems with this?)

Answer 1

Lighter than Air vs Heavier than Air - This dispute was resolved at the beginning of the 20th century by the complete victory of the latter.
In short:
It takes a VERY large amount of gas to keep the craft above the ground.
Large volume == high air resistance.
High resistance == most of the power of the engines is spent on overcoming this resistance.
To keep a device heavier than air in the air (in the end it will be lighter) requires less engine power and less energy consumption.

Answer 2

I heard that there is a shortage of helium (I don’t remember why), and now I’m launching my own quadcopter, do I need to keep a gas cylinder at home? Well, either somewhere to refuel which is not convenient. And also look at the reports where the military uses them for reconnaissance, the ball is large and noticeable from a machine gun, it’s easier to get into it, the device itself is small and almost invisible (only a buzz is heard) it’s very hard to shoot down.