If you haven’t noticed, English has rules that sometimes do not apply. Here’s an example:
It would be grammatically correct to say, “Am I not a smart person?” It does sound rather stiff and formal, but you can see that the grammar is right. However, when my son was about two, he would joke and say, “Amn’t I a smart smartypants?” Technically, he was being grammatically correct: “Am I not a smart smartypants?” So why should we say, “Aren’t I smart?” It makes no sense. We don’t say, “Are I not smart?”
In all my years of teaching English as a second language, I marveled at how any of my students were able to master the intricacies of our language. In fact, how do native speakers ever learn it? We are all smartypants!