“Physics” is just a word with an “s” at the end, not an abbreviation. “Econ” is an abbreviation for a singular concept, and doesn’t get an “s.” “Stats” is an abbreviation for a plural concept, and gets an “s.” Because “mathematics” is not the plural of “mathematic,” there’s no reason for its abbreviation to retain the vestigal “s.”Darned Brits, learn some English!
Have I ever addressed on this blog why I assert that "data" (in English, not in Latin) is singular, or why I think it's entirely reasonable to split infinitives sometimes, or to end a sentence with a preposition? If not, I'm armored up and prepared to do battle with the VLL's! (that's Victorian Luddite Linguists)