Because this one can't be ported to another platform. OUR CODE must be ported.
Another reason is that we need some special cases of stdio, adapted for concrete input/output devices. Of course it's not so important for Sprintf (but it's important for printf , fputs, etc...).
Reason number 3 is that we need all stdio&stdlib functions to be reentrant.
Reason number 4: we are curious to do this and taht's enough :)


Yes, but there are n't 32bit to ASCII or 32 bit division BY CONSTANT alghorithms. Only common division. (There is also UTIL_BINTOASC - Convert binary to ASCII function, but this one allows only )