At what age is the home you grew up in not your home anymore?

A lot of people always say “it’s HER house” or it’s “HIS” house. When referring to people living with their parents. So I was just wondering, like when a woman gives birth, the babies home is obviously with it’s mother. Same as when they’re a child or teenager. So how can a woman bring a person into the world and make it seem like they asked to live with them or something. Like they’re doing them a favor. I’ve seen kids who are like 12 and their mom is like “this is my house” and it’s like...so is your 12 year old child just homeless or something?? It’s their house too. You’re the one that chose to have them. Is it like a standard age? Like once you turn 18, your parents are doing you a favor by letting you live with them? Or is it like a situational thing