I’d say the designers were aiming for minimal cost and maximum fail‑safe. A penny is cheap, so the mechanism could use a single spring, a couple of gears and a contact sensor. Each component is cheap to source and easy to replace. By forcing the coin through a tiny “Rube Goldberg” sequence, any mis‑drop or counterfeit was almost guaranteed to be caught before the game started, so reliability was kept high without expensive electronics. The trade‑off was a lot of physical wear, but that was acceptable because coins were the only revenue source; they could replace the whole module for a few dollars once it broke. In short, cheap parts, mechanical simplicity, and built‑in redundancy made the system both low‑cost and reasonably reliable.