I've done quantitative testing on shake tables and I've not seen any situation in which split lock washers yield a benefit-- low torques, high torques, rigid assemblies, assemblies with a decent spring constant and flex in them, etc. I didn't believe that conventional wisdom could be so wrong-- but they either break even within my ability to measure or do worse.

I omit them whenever I can, now.

Tooth lock washers are pretty bad, too-- though sometimes they are slightly beneficial. I don't think they're generally worth the surface damage they cause for minimal benefit.

Mostly, you can ignore any locking device. And if you need one, a nylock nut, or a threadlocker crayon, or a wedgelocking nut, etc, is infinitely superior. (And of course, there's castellated nuts and safety wire for really critical stuff).