Genes are weird, IMO.
My mother's side of the family (everybody related to HER mother) has very thick and coarse hair they never lose.
My father's side of the family has very fine hair, and not a lot of it. The men lose what they have starting in their 30s, but it doesn't all go away so they do combovers that aren't terribly flattering.
I was born with a ridiculous amount of very fine hair. Ridiculous. Everybody who ever cut my hair (from first haircut to age 47) exclaimed that they'd never seen anything like it, just the sheer number of hairs on one head. It started going from red-brown to grey in my 20s (well, age 13 actually) and detoured through darker brown before it went all grey.
It was my best feature, easily, ha, well, my only good feature. I kept it short. Strangers would stop me to oooh and ahhhh over it. Coworkers wanted to run their hands through it. I liked it.
You're hearing the past tense part of this, right?
I was assigned female at birth. I medically transitioned to male four years ago. Two weeks into that process, my shower drain told on me - that hair is falling out. I went from dad's hair texture but mom's hair amount to... starting in aggressively on middle-aged dad's balding pattern.
DANGIT. I have ONE good physical feature and it's gone??? I mean, it's not all gone. I have a decent amount left. But now I wear a hat when it rains (couldn't feel rain before), and when the sun's out for that matter. Still got a good crop in back, but it grows pathetically slowly there, so if I want a ponytail in 2028 I'd better start now, and it's gonna get rough between here and there. More likely I'll end up shaving it off, but since my head is shaped roughly like a toaster and has lumps all over it, this ain't gonna be pretty. Oh well, got a red-brown beard out of it that my father is highly envious of because he never could grow such a thing

.