Q: Why is apostrophe so weird? Why does "Bill's" mean belonging to Bill, and "its" mean belonging to "it", but "it's" is a short-form of "it is"? Whaat?!
A: "its" is fucked. the reason it's different is because there's already an "it's", for it is. but actually both of them should logically have an apostrophe. maybe the idea is to have it be an apostropheless pronoun like 'his' or 'hers'