I'd like to think that people designing this aren't idiots - they are very well trained intelligent engineers. And probably the reason why this method was chosen was because it has some objective advantages over any other method. I don't know what those advantages might be, but I really hope they exist.

> I don't know what those advantages might be, but I really hope they exist.

The advantage is obvious: it's the most similar to how it worked back when the controls were fully mechanical.

IIRC, some old planes even had each side mechanically controlling independent halves of the control surfaces, such that the end result is the average of the inputs in case one of the control surfaces (or the cabling connecting to the controls) is jammed.