Until you can display negative numbers¹. Or have native numerals². Or need to know what the numbers even mean. :-)
__________
¹ I tend to set my minus sign to U+2212 to catch errors in code where we just use ToString() instead of ToString(CultureInfo.InvariantCulture). Almost as much fun as putting a Unicode character into your user name that isn't representable in the current legacy codepage on Windows.
² ۱۲ ۱۰ ۴ probably won't work as input to the application trying to parse that line ;)
Excuse me?