system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why did modern household drones take the form of quadrocopters?

It seems like it'd be more efficient to use the design of helicopters, having to power just two rotors instead of four ones.
gpt
Helicopters don't change the speed of their rotors to fly, they change the pitch of the blades. As you can imagine, that's kind of complicated.

Quads *do* change the speed of the rotors, not the pitch. That requires a lot of coordination between motors, but far fewer and simpler moving parts. Computers do all the flying for you. The average person can't come close to flying a conventional helicopter, but anyone can fly a quad because of the simplicity of the controls after the computer does all the heavy lifting.

Efficiency is odd...quads are actually pretty efficient. When you scale then up, they become far less so. Among other things, electric motors are very efficient at small scales, but the size of the rotors and how fast they can increase or decrease speed also matters.