If this is the case why do navies still use the conventional deck lock system?
Cost. Complexity. Crewing. Capacity.
Deck lock (known variously as Harpoon, Talon, and probably other things) consists of no moving parts on the ship. The maintenance for the ship consists of periodic cleaning and inspection of the grid and fasteners. The helicopter's system has electrical, mechanical, and hydraulic bits to it.
Beartrap (RAST) consists of lots of moving parts, requires active crewing and training on the part of the ship and maintenance of both the helicopter's and ship's parts of the system.
RAST can handle rather a lot of weight and also traverses the helicopter into the hangar. Deck lock has a lower weight limit and has no traversing function.
Deck lock can't induce inflight oscillations, RAST can. Helicopters using RAST have rolled over. A pilot can land and use deck lock unassisted. Not the case with RAST. I've used one but not the other.