The shock absorber is not only responsible to absorb power shock loads from the engine but reverse loads from the rear wheel forwards, like from a sudden stoppage like a crash or some other uncontrolled lock up. It absorbs torsional loads, just like the row of springs in a clutch plate center from a manual car. The issue with broken chains and so on is either poor maintenance, poorly fitting parts (wrong collection of parts assembly) and lastly the fact that over the years the availability of good quality chain has declined, remember what happened to the "Goodwood racer" of the Horner brothers......they could not find any decent chain, and were lucky it didn't smash out the front of their engine.........most users of these bikes should not concern themselves, it seems all too easy to "Overthink" these things.