It's the same reason we use abbreviations and contractions when speaking. A trivial simplification is still a simplification.
Why bother with Celcius at all when there is Kelvin. Even Kelvin is arbitrary. Best to use Planck normalized temperature. The scale would be absolute 0 to 100 where 0 is absolute 0 and 100 is 10^32 Kelvin.
So whenever you have to tell someone the temperature outside, you say it's 0.000000000000000000000000015237 Planck
If 3 digits isn't more a tiny bit more cumbersome than 2, then 32 digits is fine too.