Because way back when, before sensible systems, they used base-20, and despite now running base-10, the base-20 is stuck in the language.
Edit it’s sort of in most languages actually, not just to that extent. I mean, English has “twenty-one”, but no “onety-one”. 1-20 have their own numbers in most languages I think, and after twenty you just repeat the first 10 and add whatever tens you like, whereas the French sometimes repeat the first 20 and add an amount of twenties
Because way back when, before sensible systems, they used base-20, and despite now running base-10, the base-20 is stuck in the language.
Edit it’s sort of in most languages actually, not just to that extent. I mean, English has “twenty-one”, but no “onety-one”. 1-20 have their own numbers in most languages I think, and after twenty you just repeat the first 10 and add whatever tens you like, whereas the French sometimes repeat the first 20 and add an amount of twenties