Imagine dreaming of finding the one piece that Roger talked about. Then finding out later you could never do it because you didn't it the fucking GOD JESUS ALMIGHTY NIKA fruit. Luffys entire journey is due to him eating this fruit
Isn't Haki tied to will power? Maybe it blooms because when faced with uncertainty, uneven odds and impending death, one still grits through with determination to win and protect their ideals. Real life people who struggle to carry a paper bag of groceries have reportedly lifted cars to save their baby, maybe something like that for those that don't succumb to acquiescence.