Because 0°F to 100°F is way more reasonable for telling comfort than -17.78°C to 37.78°C

There is nothing more reasonable about F in that scenario. You like it because you are familiar with it, that's it. I can assure you that celsius is perfectly reasonable for telling you the room temperature. Billions of people use it without any problems, decimals and all (which is apparently something that Americans find extremely scary).