...except in one place: the kitchen. So much of kitchen work is about scaling proportions up and down. With a slide rule, this is literal child's play -- I have taught children to do it for me. You just set it once based on the key ingredient ratio and then you can immediately read off all other amounts without touching it again.
It is much easier than with any other calculation device -- as evidenced by the number of recipes I find where people hand-scrawl equivalent proportions onto them. They do that because they don't have a convenient way to scale up and down on the fly, so it's easier to make the huge effort (with an electronic calculator) once and then cache the result. (Only to have to do it again when you want to scale by a different amount.)
I honestly don't understand why a simple C/D scale slide rule with conversions on the back is standard kitchen equipment.