Not all planes were designed with control locks. Cherokee POH for example actually tells you to use seat belts.
Yes, I know, i fly them. But thats a lack of designed internal control locks (yoke pin,etc )... there is no reason someone cant by physical control locks for their plane or even make them themself. All it is is a wedge that fits in between the control surface and the the adjacent surface. Even for a piper, one wouldnt be too hard to make up if they dont make them.
On our C-123K, it has an internal control lock right next to the left seat (physically locks the cables in place), but we still put physical locks on the rudder and elevator just in case.