Why is Kirby's name written カービィ instead of カービ?

[Kazzeon]

Maybe Kirby instead of Kirbi.

I’ll link to this post of mine that just got marked as an answer for some reason.

Double vowels in katakana

There’s this question about it: Apparently, it’s so it’s Kirby instead of Kirbi, which is what I thought. But there’s not really much else in that answer.