Of course it’s a matter of convention. But it’s a convention without which the rest of mathematics taught to school children throughout the world falls apart.

Of course it’s a matter of convention. But it’s a convention without which the rest of mathematics taught to school children throughout the world falls apart. Calling the color of the sky blue is just a matter of convention as well, but if one random teacher starts calling it green, she’s doing a terrible disservice to her students. It doesn’t matter that there exists some languages without a difference between blue and green.