My wife's uncle did this. He lived with his parents until he was at least 48 or so. He worked from early in the morning until late at night for his landscaping business, rarely coming home for lunch or dinner (basically he slept there, and ate breakfast there). The house was paid off, and I think he paid the utilities and probably helped with taxes and insurance. He slept in what was his original bedroom, which was a converted garage.
He finally moved out and got his own place a few years back, and probably paid cash for it.
Well, I don’t want him around until he is 48. But he is welcome to get his feet under him after school before diving in and living in debt his whole life.
My dad had a family business, so you stayed at home or near home after 18 because you were still working on the land, so it isn’t so strange to me. My brother’s didn’t really move out until they got married.