It seems to me that the most common general use of these units is to describe ambient outdoor temperatures, and while I admit that I haven't traveled widely, I'd be astonished to discover that most countries outside the US have physical environments more reminiscent of, say, Mercury or Venus, than what we in the US parochially consider to be Earth's standard range of atmospheric temperatures.

I suppose that's why I consider Fahrenheit to be a very appropriate scale - since it centers nicely on the range of temperatures one might actually experience on Earth, naively assuming that America is representative of the rest of the planet - and isn't quite so arbitrary as one indexed to the temperature of boiling water, a phenomenon which a person in America - and, presumptuously, the rest of the Earth - isn't likely to encounter without having intentionally induced it.

But perhaps -15 and 40 really are more sensible positions for roughly opposite extremes, and we really are the odd ones for using 0 and 100.

Could you explain what you mean? I think my comment does a pretty good job of demonstrating that the scalig is nicely suited to the temperatures a human being experiences over the course of each year.

The main problem comes with negative Celsius temperature (basically 32F) as freezing point is quite important traffic wise. Driving on ice/snow is quite a change and basically occurs around 33F-32F, in Celsius it that's zero, much easier to remember.

Then you have 100F which is supposed to be the normal body temperature, but actually it means having fever.

There is only one case you might wish to use a tenth of Celsius in every day life and that's reporting body temperature around 37C-39C.

Like I've said, scaling is weird, it doesn't make much sense when firstly introduced. I have a friend who graduated MIT (PhD in aerospace engineering), living in the US for over 10 years and he is comfortable doing calculations and every day estimations in imperial units, except for temperature.

If you had to use decimals in Celsius for everyday measurements then you might have a point, but since you generally don't it really doesn't make a difference.

There's easily enough precision in the Celsius scale for everyday measurements, so it all comes down to what you're used to.