You're explaining that poorly, I think.  As written, that's only true if 99% of all software is written using poor algorithm choices.  Maybe that's true in some regimes, but there is still a bunch of performance-sensitive software written in C/C++ by developers who make good algorithm and data structure choices.<p>And so when these people get to looking at performance details, they're looking at constant factor improvements.  And as described in the article and elsewhere, the constant factors due to cache effects are often on the order of, say, 6 or 10.  The penalty to poor cache design can be huge, and it's important to know how they work to avoid that.