It used to be machinery was vastly overbuilt, almost because there wasn't any practical means to micromanage design, but there was also a certain pride taken in what was built. Somewhere in the 70's some yutz decided torque ratings were the way to go. And thereafter you got engines, transmissions and every manner of things that were just barely up to the job. No overhead was contemplated....of course generous overhead is what absorbs shock loads, and creates long term dependability. This design ethic permeates everything because building close to theoretical ratings is cheaper than just building it as strong as you can make it. Suppliers may be supplying inferior goods, but the designs they are given are crippled from the drawing board. We seem to get mostly reliable bikes, but occasionally we get a dud.