While I was doing my Millwright Apprenticeship,some twenty years ago, we had a gentleman come into class and give a demonstration on this exact same thing. He proved that lock washers were nothing but a warm fuzzy feeling for the people that used them. So we asked why are they made and sold if they don't work? His answer....because the customers want them.
He also showed with another piece of equipment that it's more important to torque a threaded fastener to the proper specs if you don't want it to fall apart. And if the fastener is torqued to the proper specs once and disassembled it will break before being able to be retorqued to the proper specs the second time.
Trouble is not everybody has a torque wrench handy when putting threaded fasteners together. And that's why they make all the anerobic thread lockers of various strengths.
Jerry