It's simple pragmatism. If you can't effectively communicate with people in the place you're going to live, it's going to cause problems. I can't walk into a math class and say, "I'm going to use Ø instead of +, ╩ for -, ≡ for 2, ▬ for integration, and for multiplication."
I doubt you'd be able to sue for discrimination if they'd insist that you use conventional mathematical symbols.
English is (was?) the primary language in the US, though it seems that even that's getting bastardized more and more by people who are too lazy and stupid to learn proper grammars and punctuationality...ness.