Split lock washers do nothing?

Where a split washer was properly installed, removal will find where it bit into and created a tooth in the softer material. Another factor in failures today is the quality of materials the lock washers are made of. Good American made steel is kind of rare and very expensive today. What we find and can afford to buy is imported modern alloy mixes. As a plant maintenance mechanic the very first best example we found was in allen socket head set screws and allen hex keys/wrenches. Approx' 1980.
Just FYI , Today NASA ( us taxpayers ) pays about 11 USD for a single 3/16 allen wrench.