The crusty old electrician who taught me to solder when I was nine made me practice this splice, along with the rat-tail and the T-splice and a couple of others, and I'll never forget it. I've rarely needed to use it, however, since domestic wiring has been all about Romex and wire-nuts for decades now, and in the low-voltage electronics context where I've done most of my soldering, putting any strain on a wire joint is a recipe for suffering.
A wire splice that will not pull apart, suitable for both dry and soldered applications. Every hacker should know this.