I believe it is a Samoan thing. Kalani’s Mother herself isn’t Samoan but married a very opinionated, domineering Samoan man who probably decreed she should grow her hair long and their daughters grew up following the long hair culture. I was reading a bit about it and there was something about in Samoa cutting your long hair was considered “spoiling your beauty”. Also, larger, buxom wives are seen as a symbol of prosperity. Kalani might not have had many suitors in Utah but when she went to Samoa, she was exactly Asuelu’s type.