Why does for...in fail gracefully but for...of throw an Exception?

Question

Why is it that

for (let e in null) void e

fails gracefully, but that

for (let e of null) void e

throws a TypeError? Doesn't this result in an inconsistency?

Answer 1

for...of only works on iterable objects (i.e. objects implementing iterable protocol) which null is not either of these. Whereas for...in works on all values.