I believe it is a combination of genetics and taking good care of their hair. Here is why I think this my sister had waist length hair as a child and as an adult she has BSL. My sister's cousin (my sister is tech. my half-sister) has hair down to her tailbone as an adult. My sister and her cousin have 4a hair. My sister and I had an aunt that had hair down to her tailbone. Most of the women on my mom's side of family have Sl or longer hair. On my father's side of the family I am and always the one with the longest hair even when I had a chin length bob
erplexed. Anyway, since long hair is present on both sides of my sister's family, I believe my sister and people like her are more destined to have long hair.
I have noticed that women with long hair take better care of their hair and have a more positive attitude towards their hair. My sister was the first person to introduce me to protective styling(buns and french rolls), roller setting, caruso, and washing once a week. Her cousin was the first person I saw that simple french braided her daughter's hair instead of the tight braids. Her daughter now has waist length hair.
women with long hair have a tendency to have daughters with long hair. I have also noticed that mothers with long hair avoid hair trends popular with blacks, no tight braids, no relaxers or reduce the number of times to get a relaxer or the strength of the relaxer. Women with long hair sometimes sarcifrice style for health/length. They are not h**l bent on removing every wave, kink, or curl.
I would not compare us to latinas or Indians because most of them had long hair as a child and they rarely cut their hair short. Short to them is APL.