Knuth has lost almost all meaning in more heads than Sturgeon’s Law would anticipate. Too often his quote is just an excuse for developers not to think.

    There is no doubt that the grail of effi-
    ciency leads to abuse. Programmers waste
    enormous amounts of time thinking about,
    or worrying about, the speed of noncritical
    parts of their programs, and these attempts
    at efficiency actually have a strong negative
    impact when debugging and maintenance are
    considered. We should forget about small
    efficiencies, say about 97% of the time: pre-
    mature optimization is the root of all evil.
    Yet we should not pass up our opportuni-
    ties in that critical 3 %. A good programmer
    will not be lulled into complacency by such
    reasoning, he will be wise to look carefully
    at the critical code; but only after that code
    has been identified. It is often a mistake to
    make a priori judgments about what parts
    of a program are really critical, since the
    universal experience of programmers who
    have been using measurement tools has been
    that their intuitive guesses fail.

> A good programmer will not be lulled into complacency by such reasoning

And yet “lulled into complacency” is exactly what most people are.