Its not the wrong unit, we just forgot how to update it and its working well enough. Also bite me I dont want to deal with decimals to know the tempeture on a more accurate level.
Various groups in the US have tried to convert and it failed because... There's absolutely nothing wrong with the current system and very, very little to be gained by switching.
Also if the US actually switched, what would all the people who comment and complain about it on the Internet do with all of that free time? Get a hobby? Or start lobbying the whole world to switch to Kelvin?
I also realized my american appliance do this same when I try to set them to celsius (nest etc). I guess that is where this unfortunate misconception comes from.