Because libcs other than glibc are less bloated and probably easier to read.

  ~ $ cat empty.c
  int main(void) {return 42;}

  ~ $ gcc -static empty.c -O3
  ~ $ strip a.out
  ~ $ size
     text	   data	    bss	    dec	    hex	filename
   677598	   5792	  10464	 693854	  a965e	a.out

  ~ $ diet gcc -static empty.c -O3
  ~ $ strip a.out
  ~ $ size
     text	   data	    bss	    dec	    hex	filename
      901	     32	     76	   1009	    3f1	a.out

It's just not very readable.