Cold and warm are relative. 0 for freezing / snowing and 100 for boiling gives you a much more understandable range. Honestly, US metrics don’t make any kind of sense anymore...

Except for weather, it’s never 100 C outside, or else we’d all die.

Yeah but it's still a very useful point where 100 should be, e.g. when you go to a sauna you know more precisely what to expect.

While it's true that 100C doesn't have any weather meaning, 0F being "very cold" isn't particularly objective. I just looked it up, and apparently 0F is only about -18C. Whether -18C is "very, very cold" depends a lot on where you're from and what you're used to. I'm Canadian and I certainly wouldn't characterize -18C as "very, very cold". -30C maybe. 0C has a fairly objective interpretation in terms of weather: it's the point at which puddles start to freeze into ice slicks.

Canada is a very cold country ;)

Yes, they are relative. 0 for freezing and 100 for boiling works well for chemical reactions and cooking. 0 for extremely cold weather and 100 for extremely hot weather works well for knowing what to wear before going outside. Celsius requires smaller numbers with decimals for similar weather precision.