this rule only applies for je / jij, but not for jou (because jou can only be in object position) or jouw (because jouw is your, so it needs a noun to follow, so it's actually third person, for example, jouw moeder = ze, or jouw zoon = hij). Remember that je, when it preceeds a noun, means jouw (so you could say je kat) - that's the unmarked form of jouw*.
So it needs to be waarom draagt jouw kat een hoed?
I'm upvoting your comment, because someone downvoted it.
Please, people, don't downvote comments when someone is a little bit confused. Instead, be kind and help them understand why they're confused, so they can go further in their learning process. Read Vygotsky!
Hope this helps!
I suppose you think Americans are crazy however the rich Americans actually have wardrobes for their cat and dog pets not just beds and houses they actually have four jobs some of them paint their dogs fur which I think is actually going a step too far they do have boots because in the cold weather that ice gets up in their toes and it makes them very cold there are a lot of things that people in America do to keep their animals either in style or warm I know it's crazy but it does have some practical uses