The -40C was a typo, should have been 40C, to mirror the 0F to 100F, rounding a bit to make it less silly. It’s been fixed now.
Millions do experience 0F, and it’s ok to not use the full range. At or around 0F is cold, as you move closer or beyond it, it’s cold. As you move closer to or beyond 100F, it’s hot. Most people would likely prefer to never deal with <0F or >100F.
Millions -- hundreds of millions, even -- regularly experience -10F and 110F as well, but you've arbitrarily picked 0F-100F, so I guess their experience doesn't matter, because you prefer round numbers?
I experienced 3°F in the subtropics and it is probably about 100°F outside right now. Average winter temps of 35° with only 1-7 days of actual frost, usually around christmas. (Dec 25(December 25))
Most people never experience anywhere near 0F in their lives.
> -20C to -40C seems much more arbitrary as a way to measure the zone humans mostly live in.
The zone most humans live in does not routinely (if ever) get anywhere near -20, to say nothing of -40.