[cle]

Because everyone has different emotions, preconceptions, etc. attached to the existing word. Introduce a new one, and you can define what it means without worrying about people misunderstanding you (unless they already know what Ikigai is, and I’d be willing to bet in that case that they’d disagree with the author’s over-simplification or mischaracterization of the word). There’s also an “exotic” attraction to concepts from other cultures.