0-100F is not base 10 at all,

Umm, yes, it is. Zero and a hundred, and convention is to break up temperatures like “it’s in the forties”. It’s all base 10.

TV weather people saying that the temp will be in the 80s is less useful to me than if they tell me if it will be 27°C for example

Is it going to be 27C all day long? Is it going to be between 80 and 90 all day long? One is more likely than the other, and even if it’s 78 in the morning, that’s fine, doesn’t make much difference.

Here, C is overly precise for the task.

Why would you do ±1°C if the sous vide can do decimals?

Because 130, a number with a zero at the end of it, is easier to deal with than 54.4.

This has an effect on UI, as well. Two buttons for going up or down. With F, you can do that in 1 or 0.5 degree increments. In C, it’d have to be 0.1, and you’re pressing it more to get to where you want.

Also, the recipe calls for 130°F because it was made by an American, if you look for European recipes it will probably say 54°C.

Which will be wrong. Steak turns out differently with slight changes in temperature around this level. European recipes will have to go to 54.4C.

Neither will add decimals to their recipes because that’s just being anal

No, it’s using sous vide properly. Precision is why you do it.