At some point, Mr. Cows, an assembly or artefact has to terminate. There are only so many ways to connect things together in a manner that can be dissembled and rebuilt. There is also only so much material and weight that can be used and included too. I think all methods have been tried by now!
If a split pin and a lockwired nut on an assembly of high quality design and material fail, on the back of proper maintenance and inspection, then one really is subject to the worst of probability.