The current rules for its and it's do not make zero sense.
Explain to me the sense of why one has an apostrophe and the other does not, and why it's not the other way around.
Contractions with pronouns and forms of helping verbs, including
be, always have apostrophes standing in for the omitted letters—for example,
he's, she's, I'm, they're, we'll, you've and so on. There aren't any exceptions to this rule, so there's nothing nonsensical about that.
Possessive forms of personal, interrogative, and relative pronouns never have apostrophes. Of course, the only ones that end in
s are
his and whose, and even though these historically comes from
he or
who plus the genitive
s inflection, morphologically it's not really the same as the possessive
s that we attach to other things. The question is whether
it is still considered a personal pronoun and whether the
s on the possessive form is the same as the one on
his and
whose or something else. You could make a good argument that
its is just
it plus the possessive
's enclitic, just like
one's. So that's where it's debatable and maybe a little nonsensical (though not completely nonsensical).
