NavList:

Frank wrote

Why not? Why aren't people using slide rules? Obviously, basic electronic calculators are dirt cheap. Even for addition, most people today under the age of, perhaps, fifty use calculators and really can't get by without one. Calculators are familiar, cheap, more accurate, faster, and easier to use.

The question isn't "why aren't people using slide rules"? It is why aren't people using logs or long multplication? When the decision has been made not to use logs or long multiplication then the pocket calculator is the sensible choice. It is the digital version of the analogue slide rule. I have a slide rule but in the past four or so decades have never considered using it for multiplication. Instead  I use a calculator.

Slide rules are used by slide rule enthusiast just as CN is performed by CN enthusiasts. CN by slide rule is done by those who are both slide rule and CN enthuiasts.

If I owned a Bygrave I would probably reduce sights by slide rule but I am not fortunate to own one so a calculator or tables is my choice.