Even if people didn’t know just what it did, perhaps they thought a double action must be better than a mere single action. Sort of how we buy razors with four blades, when we were shaving perfectly fine with three blades, or even a mere two, before that.
Here’s a random question I’ve asked myself: if someone does make a harp where the body is made of a very strong but lightweight materials, and the action stays the same on top, could the harp become top-heavy and prone to tipping without some additional weight put back in for balance?