That's right. Even American think so, that's also interesting.thank you for your comments.

There is no reason. English spellings are confusing with many words.

Thank you so much!

We spell it that way because the state of Hawaii derives its name from the name of its largest island, Hawaiʻi. The native Polynesian inhabitants called it that in their language. Later, after losing its sovereignty, the name gradually just became Hawaii, without the diacritic mark. I hope that this helps you. J.