The C code `printf("%ls", L"αβγ");` prints nothing at all, why is that?

Question

I know L prefix indicates a string literal.

This code

#include <stdio.h>

int main()
{
    printf("%ls", L"abc");
    return 0;
}

prints the string literal "abc" verbatim while the following code

printf("%ls", L"αβγ");

gives nothing, although simple string

printf("αβγ");

can be displayed well, why is that?