I wouldn't think it's that unusual, but "better off" depends on a lot of factors that differ between individuals and is partially subjective.
As others said, it's nice if they feel welcome and everything is going well, but I would find it odd if young adults didn't have plans for the future involving moving out even if it's not likely in the near future. Maybe that's because as a teenager, pretty much everyone I knew were all about moving away, but two decades on, a lot of people haven't really made it yet... I find that odd, but not unusual, I guess if that makes sense.
not sure everybody would agree that you have any real independence if you already settle with your husband (to be) from the age of 21!
How would moving in with flatmates as being repeatedly suggested by more real independent than moving in with a partner one ends up marrying? It's not that unusual for flatmates to start dating, even marrying.
I guess this depends on how people define 'real' independence.
I mean, I immigrated and married at 18. I'm sure people could come up with an argument I wasn't independant or free, but I certainly was from my parents which I would think is the main concern here. With most of my peers who, even when living on their own, were regularly getting money from their parents to support their young freedom, I certainly felt more independent than them or in what was essentially living on my own but under my parents' roof and juggling their financial messes (working with the electric company when they'd come to shut off the power when I was 15 and home alone was a formative experience I wouldn't wish on anyone) that ahppened before I was kicked out. I didn't get much choice when I left (lovely finishing school present), but part of the freedom for me was choosing to live with other people who would actually be there. 'Settling down' was freedom to me.
Even well into my thirties, I know plenty of 'independent' people who regularly get financial and practical support from family that I haven't had since well before I left home. Where I am, that seems pretty usual even if to me it's odd. We could really narrow down who is really independent if we cut out anyone who lives with others and gets any sort of outside help to something even less achievable to most young adults.