In "Insanely Great," a history of the Macintosh computer written by Steven Levy, author of the famous book "Hackers", Levy tells how Steve Jobs, then head of Macintosh development in Apple Computer, pushed his programmers to shave seconds off the boot time of the computer. Jobs did calculations based on how many millions of people he thought would buy and used Macintoshes and how many times they would boot their computers every year, and came up with the fact that shaving 2 seconds off the boot time would save many centuries of human waiting time and frustration. Of course, no one human would ever have access to all those saved-up seconds, but never mind.

The very first FORTRAN compiler was full of sophisticated optimizations that produced excellent assembly code, almost as good as the best human assembler programmers, because the development team thought people would not use FORTRAN unless the programs it produced were almost as fast as what humans could write. Nowadays, nobody would dream of going back to assembly programming full-scale, but every little bit of time saved helps.