It's just a rule. You may as well ask why English doesn't have gender.
In some rare cases, this rule can be broken. "My every (noun)" is sometimes acceptable.
Usually, these kinds of sentences are phrased differently in English. For example, we might say "That (noun) of yours" or "Any (noun) of theirs" or "Some (noun) of mine". Unfortunately, this is not allowed with "one's" or "whose".
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