First of all, that has nothing to do with the UNIX philosophy, second of all, it has nothing to do with type theory. Anyone is perfectly capable of implementing a Maybe/Option/whatever type in C, allocating it on the heap (because you wouldn't be able to return it if it were stack-allocated), and then returning a pointer to it, whereupon C's actual type system would happily complain about mismatched types if you tries to use this type without deliberately accessing its internal members, at which point you're doing exactly as much intentional effort as if you used a convenient accessor macro that checks to make sure it's not the nil case. While I agree that C (and its type system) could be much better, fixing the problem is not quite as simple as "just design a better type system".