Thank you! I think now I’ve understood why—to let all users distinguish notes of any tuning whichever font they’re using, default of not(?)
Then here’s another idea: maybe it’s possible to add some ASCII chars to default font? As one can derive, at least 10 ‘codepoints’ are free in the bitmap [4 in the column with hexadecimal digits and 3 in each of two columns with letters at the right side], of course if they aren’t reserved for other uses.

I see there are more than 10 characters left in ASCII and different people may want to have different ones. So if this idea is sensible then later we maybe can discuss in another thread which of them are of more interest to most people.