Definitely ethnic variations. I've known plenty of people who are relatively new to the US and still hold a lot of their previous customs about the living arrangements of children and young adults.

My impression is that most Americans look at it and say "that's different", but don't look down on it.

there are ethic variations if not some that developed regionally. however a lot also deals with perceptions built up over time. Farm communities tend to see this for farms passing to the next generation.

The college industry is big money and they are incessant in their message that if you spend tens of thousands you will be a success. This implies that those who don't are not trying or worse.